Context for coding affine mode adaptive motion vector resolution

ABSTRACT

A method for video processing is provided. The method includes determining that a conversion between a current video block of a video and a coded representation of the current video block is based on a non-affine inter AMVR mode; and performing the conversion based on the determining, wherein the coded representation of the current video block is based on a context based coding, and wherein a context used for coding the current video block is modeled without using an affine AMVR mode information of a neighboring block during the conversion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/229,064, filed on Apr. 13, 2021, which is a continuation ofInternational Patent Application No. PCT/CN2020/074122, filed on Jan.31, 2020, which claims the priority to and benefits of InternationalPatent Application No. PCT/CN2019/074216, filed on Jan. 31, 2019, andPCT/CN2019/074433, filed on Feb. 1, 2019, and PCT/CN2019/079962, filedon Mar. 27, 2019. All the aforementioned patent applications are herebyincorporated by reference in their entireties. TECHNICAL FIELD

This patent document relates to video processing techniques, devices andsystems.

BACKGROUND

In spite of the advances in video compression, digital video stillaccounts for the largest bandwidth use on the internet and other digitalcommunication networks. As the number of connected user devices capableof receiving and displaying video increases, it is expected that thebandwidth demand for digital video usage will continue to grow.

SUMMARY

Devices, systems and methods related to digital video coding, andspecifically, to motion vector predictor derivation and signaling foraffine mode with adaptive motion vector resolution (AMVR) are described.The described methods may be applied to both the existing video codingstandards (e.g., High Efficiency Video Coding (HEVC)) and future videocoding standards or video codecs.

In one representative aspect, the disclosed technology may be used toprovide a method for video processing. This method includes determiningthat a conversion between a current video block of a video and a codedrepresentation of the current video block is based on a non-affine interAMVR mode; and performing the conversion based on the determining, andwherein the coded representation of the current video block is based ona context based coding, and wherein a context used for coding thecurrent video block is modeled without using an affine AMVR modeinformation of a neighboring block during the conversion.

In another representative aspect, the disclosed technology may be usedto provide a method for video processing. This method includesdetermining that a conversion between a current video block of a videoand a coded representation of the current video block is based on anaffine adaptive motion vector resolution (affine AMVR) mode; andperforming the conversion based on the determining, and wherein thecoded representation of the current video block is based on a contextbased coding, and wherein a variable controls two probability updatingspeeds for a context.

In another representative aspect, the disclosed technology may be usedto provide a method for video processing. This method includesdetermining that a conversion between a current video block of a videoand a coded representation of the current video block is based on anaffine AMVR mode; and performing the conversion based on thedetermining, and wherein the coded representation of the current videoblock is based on a context based coding, and wherein a context used forcoding the current video block is modeled using a coding information ofa neighboring block for which an AMVR mode of both affine inter mode andnormal inter mode is used during the conversion.

In another representative aspect, the disclosed technology may be usedto provide a method for video processing. This method includesdetermining, for a conversion between a current video block of a videoand a coded representation of the current video block, a usage ofmultiple contexts for the conversion; and performing the conversionbased on the determining, and wherein the multiple contexts are utilizedfor coding a syntax element indicating a coarse motion precision

In another representative aspect, the disclosed technology may be usedto provide a method for video processing. This method includes: making adetermination, for a conversion between a current video block of a videoand a coded representation of the current video block, whether to use asymmetric motion vector difference (SMVD) mode based on a currentlyselected best mode for the conversion; and performing the conversionbased on the determining.

In another representative aspect, the disclosed technology may be usedto provide a method for video processing. This method includes: making adetermining, for a conversion between a current video block of a videoand a coded representation of the current video block, whether to use anaffine SMVD mode based on a currently selected best mode for theconversion; and performing the conversion based on the determining.

In another representative aspect, the above-described method is embodiedin the form of processor-executable code and stored in acomputer-readable program medium.

In yet another representative aspect, a device that is configured oroperable to perform the above-described method is disclosed. The devicemay include a processor that is programmed to implement this method.

In yet another representative aspect, a video decoder apparatus mayimplement a method as described herein.

The above and other aspects and features of the disclosed technology aredescribed in greater detail in the drawings, the description and theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of constructing a merge candidate list.

FIG. 2 shows an example of positions of spatial candidates.

FIG. 3 shows an example of candidate pairs subject to a redundancy checkof spatial merge candidates.

FIGS. 4A and 4B show examples of the position of a second predictionunit (PU) based on the size and shape of the current block.

FIG. 5 shows an example of motion vector scaling for temporal mergecandidates.

FIG. 6 shows an example of candidate positions for temporal mergecandidates.

FIG. 7 shows an example of generating a combined bi-predictive mergecandidate.

FIG. 8 shows an example of constructing motion vector predictioncandidates.

FIG. 9 shows an example of motion vector scaling for spatial motionvector candidates.

FIG. 10 shows an example of motion prediction using the alternativetemporal motion vector prediction (ATMVP) algorithm for a coding unit(CU).

FIG. 11 shows an example of a coding unit (CU) with sub-blocks andneighboring blocks used by the spatial-temporal motion vector prediction(STMVP) algorithm.

FIGS. 12A and 12B show example snapshots of sub-block when using theoverlapped block motion compensation (OBMC) algorithm.

FIG. 13 shows an example of neighboring samples used to deriveparameters for the local illumination compensation (LIC) algorithm.

FIG. 14 shows an example of a simplified affine motion model.

FIG. 15 shows an example of an affine motion vector field (MVF) persub-block.

FIG. 16 shows an example of motion vector prediction (MVP) for theAF_INTER affine motion mode.

FIGS. 17A and 17B show examples of the 4-parameter and 6-parameteraffine models, respectively.

FIGS. 18A and 18B show example candidates for the AF_MERGE affine motionmode.

FIG. 19 shows an example of bilateral matching in pattern matched motionvector derivation (PMMVD) mode, which is a special merge mode based onthe frame-rate up conversion (FRUC) algorithm.

FIG. 20 shows an example of template matching in the FRUC algorithm.

FIG. 21 shows an example of unilateral motion estimation in the FRUCalgorithm.

FIG. 22 shows an example of an optical flow trajectory used by thebi-directional optical flow (BIO) algorithm.

FIGS. 23A and 23B show example snapshots of using of the bi-directionaloptical flow (BIO) algorithm without block extensions.

FIG. 24 shows an example of the decoder-side motion vector refinement(DMVR) algorithm based on bilateral template matching.

FIGS. 25A to 25F show flowcharts of example methods for video processingbased on some implementations of the disclosed technology.

FIG. 26 is a block diagram of an example of a hardware platform forimplementing a visual media decoding or a visual media encodingtechnique described in the present document.

FIG. 27 shows an example of symmetrical mode.

FIG. 28 shows another block diagram of an example of a hardware platformfor implementing a video processing system described in the presentdocument.

DETAILED DESCRIPTION

Due to the increasing demand of higher resolution video, video codingmethods and techniques are ubiquitous in modern technology. Video codecstypically include an electronic circuit or software that compresses ordecompresses digital video, and are continually being improved toprovide higher coding efficiency. A video codec converts uncompressedvideo to a compressed format or vice versa. There are complexrelationships between the video quality, the amount of data used torepresent the video (determined by the bit rate), the complexity of theencoding and decoding algorithms, sensitivity to data losses and errors,ease of editing, random access, and end-to-end delay (latency). Thecompressed format usually conforms to a standard video compressionspecification, e.g., the High Efficiency Video Coding (HEVC) standard(also known as H.265 or MPEG-H Part 2) [1], the Versatile Video Codingstandard to be finalized, or other current and/or future video codingstandards.

Embodiments of the disclosed technology may be applied to existing videocoding standards (e.g., HEVC, H.265) and future standards to improvecompression performance. Section headings are used in the presentdocument to improve readability of the description and do not in any waylimit the discussion or the embodiments (and/or implementations) to therespective sections only.

1. Examples of Inter-Prediction in HEVC/H.265

Video coding standards have significantly improved over the years, andnow provide, in part, high coding efficiency and support for higherresolutions. Recent standards such as HEVC and H.265 are based on thehybrid video coding structure wherein temporal prediction plus transformcoding are utilized.

1.1 Examples of Prediction Modes

Each inter-predicted PU (prediction unit) has motion parameters for oneor two reference picture lists. In some embodiments, motion parametersinclude a motion vector and a reference picture index. In otherembodiments, the usage of one of the two reference picture lists mayalso be signaled using inter_pred_idc. In yet other embodiments, motionvectors may be explicitly coded as deltas relative to predictors.

When a CU is coded with skip mode, one PU is associated with the CU, andthere are no significant residual coefficients, no coded motion vectordelta or reference picture index. A merge mode is specified whereby themotion parameters for the current PU are obtained from neighboring PUs,including spatial and temporal candidates. The merge mode can be appliedto any inter-predicted PU, not only for skip mode. The alternative tomerge mode is the explicit transmission of motion parameters, wheremotion vector, corresponding reference picture index for each referencepicture list and reference picture list usage are signaled explicitlyper each PU.

When signaling indicates that one of the two reference picture lists isto be used, the PU is produced from one block of samples. This isreferred to as ‘uni-prediction’. Uni-prediction is available both forP-slices and B-slices [2].

When signaling indicates that both of the reference picture lists are tobe used, the PU is produced from two blocks of samples. This is referredto as ‘bi-prediction’. Bi-prediction is available for B-slices only.

1.1.1 Embodiments of Constructing Candidates for Merge Mode

When a PU is predicted using merge mode, an index pointing to an entryin the merge candidates list is parsed from the bitstream and used toretrieve the motion information. The construction of this list can besummarized according to the following sequence of steps:

Step 1: Initial candidates derivation

-   -   Step 1.1: Spatial candidates derivation    -   Step 1.2: Redundancy check for spatial candidates    -   Step 1.3: Temporal candidates derivation

Step 2: Additional candidates insertion

Step 2.1: Creation of bi-predictive candidates

Step 2.2: Insertion of zero motion candidates

FIG. 1 shows an example of constructing a merge candidate list based onthe sequence of steps summarized above. For spatial merge candidatederivation, a maximum of four merge candidates are selected amongcandidates that are located in five different positions. For temporalmerge candidate derivation, a maximum of one merge candidate is selectedamong two candidates. Since constant number of candidates for each PU isassumed at decoder, additional candidates are generated when the numberof candidates does not reach to maximum number of merge candidate(MaxNumMergeCand) which is signalled in slice header. Since the numberof candidates is constant, index of best merge candidate is encodedusing truncated unary binarization (TU). If the size of CU is equal to8, all the PUs of the current CU share a single merge candidate list,which is identical to the merge candidate list of the 2N×2N predictionunit.

1.1.2 Constructing Spatial Merge Candidates

In the derivation of spatial merge candidates, a maximum of four mergecandidates are selected among candidates located in the positionsdepicted in FIG. 2. The order of derivation is A₁, B₁, B₀, A₀ and B₂.Position B₂ is considered only when any PU of position A₁, B₁, B₀, A₀ isnot available (e.g. because it belongs to another slice or tile) or isintra coded. After candidate at position A₁ is added, the addition ofthe remaining candidates is subject to a redundancy check which ensuresthat candidates with same motion information are excluded from the listso that coding efficiency is improved.

To reduce computational complexity, not all possible candidate pairs areconsidered in the mentioned redundancy check. Instead only the pairslinked with an arrow in FIG. 3 are considered and a candidate is onlyadded to the list if the corresponding candidate used for redundancycheck has not the same motion information. Another source of duplicatemotion information is the “second PU” associated with partitionsdifferent from 2N×2N. As an example, FIGS. 4A and 4B depict the secondPU for the case of N×2N and 2N×N, respectively. When the current PU ispartitioned as N×2N, candidate at position A₁ is not considered for listconstruction. In some embodiments, adding this candidate may lead to twoprediction units having the same motion information, which is redundantto just have one PU in a coding unit. Similarly, position B₁ is notconsidered when the current PU is partitioned as 2N×N.

1.1.3 Constructing Temporal Merge Candidates

In this step, only one candidate is added to the list. Particularly, inthe derivation of this temporal merge candidate, a scaled motion vectoris derived based on co-located PU belonging to the picture which has thesmallest POC difference with current picture within the given referencepicture list. The reference picture list to be used for derivation ofthe co-located PU is explicitly signaled in the slice header.

FIG. 5 shows an example of the derivation of the scaled motion vectorfor a temporal merge candidate (as the dotted line), which is scaledfrom the motion vector of the co-located PU using the POC distances, tband td, where tb is defined to be the POC difference between thereference picture of the current picture and the current picture and tdis defined to be the POC difference between the reference picture of theco-located picture and the co-located picture. The reference pictureindex of temporal merge candidate is set equal to zero. For a B-slice,two motion vectors, one is for reference picture list 0 and the other isfor reference picture list 1, are obtained and combined to make thebi-predictive merge candidate.

In the co-located PU (Y) belonging to the reference frame, the positionfor the temporal candidate is selected between candidates C₀ and C₁, asdepicted in FIG. 6. If PU at position C₀ is not available, is intracoded, or is outside of the current CTU, position C₁ is used. Otherwise,position C₀ is used in the derivation of the temporal merge candidate.

1.1.4 Constructing Additional Types of Merge Candidates

Besides spatio-temporal merge candidates, there are two additional typesof merge candidates: combined bi-predictive merge candidate and zeromerge candidate. Combined bi-predictive merge candidates are generatedby utilizing spatio-temporal merge candidates. Combined bi-predictivemerge candidate is used for B-Slice only. The combined bi-predictivecandidates are generated by combining the first reference picture listmotion parameters of an initial candidate with the second referencepicture list motion parameters of another. If these two tuples providedifferent motion hypotheses, they will form a new bi-predictivecandidate.

FIG. 7 shows an example of this process, wherein two candidates in theoriginal list (710, on the left), which have mvL0 and refIdxL0 or mvL1and refIdxL1, are used to create a combined bi-predictive mergecandidate added to the final list (720, on the right).

Zero motion candidates are inserted to fill the remaining entries in themerge candidates list and therefore hit the MaxNumMergeCand capacity.These candidates have zero spatial displacement and a reference pictureindex which starts from zero and increases every time a new zero motioncandidate is added to the list. The number of reference frames used bythese candidates is one and two for uni- and bi-directional prediction,respectively. In some embodiments, no redundancy check is performed onthese candidates.

1.1.5 Examples of Motion Estimation Regions for Parallel Processing

To speed up the encoding process, motion estimation can be performed inparallel whereby the motion vectors for all prediction units inside agiven region are derived simultaneously. The derivation of mergecandidates from spatial neighborhood may interfere with parallelprocessing as one prediction unit cannot derive the motion parametersfrom an adjacent PU until its associated motion estimation is completed.To mitigate the trade-off between coding efficiency and processinglatency, a motion estimation region (MER) may be defined. The size ofthe MER may be signaled in the picture parameter set (PPS) using the“log 2_parallel_merge_level_minus2” syntax element. When a MER isdefined, merge candidates falling in the same region are marked asunavailable and therefore not considered in the list construction.

1.2 Embodiments of Advanced Motion Vector Prediction (AMVP)

AMVP exploits spatio-temporal correlation of motion vector withneighboring PUs, which is used for explicit transmission of motionparameters. It constructs a motion vector candidate list by firstlychecking availability of left, above temporally neighboring PUpositions, removing redundant candidates and adding zero vector to makethe candidate list to be constant length. Then, the encoder can selectthe best predictor from the candidate list and transmit thecorresponding index indicating the chosen candidate. Similarly withmerge index signaling, the index of the best motion vector candidate isencoded using truncated unary. The maximum value to be encoded in thiscase is 2 (see FIG. 8). In the following sections, details aboutderivation process of motion vector prediction candidate are provided.

1.2.1 Examples of Constructing Motion Vector Prediction Candidates

FIG. 8 summarizes derivation process for motion vector predictioncandidate, and may be implemented for each reference picture list withrefidx as an input.

In motion vector prediction, two types of motion vector candidates areconsidered: spatial motion vector candidate and temporal motion vectorcandidate. For spatial motion vector candidate derivation, two motionvector candidates are eventually derived based on motion vectors of eachPU located in five different positions as previously shown in FIG. 2.

For temporal motion vector candidate derivation, one motion vectorcandidate is selected from two candidates, which are derived based ontwo different co-located positions. After the first list ofspatio-temporal candidates is made, duplicated motion vector candidatesin the list are removed. If the number of potential candidates is largerthan two, motion vector candidates whose reference picture index withinthe associated reference picture list is larger than 1 are removed fromthe list. If the number of spatio-temporal motion vector candidates issmaller than two, additional zero motion vector candidates is added tothe list.

1.2.2 Constructing Spatial Motion Vector Candidates

In the derivation of spatial motion vector candidates, a maximum of twocandidates are considered among five potential candidates, which arederived from PUs located in positions as previously shown in FIG. 2,those positions being the same as those of motion merge. The order ofderivation for the left side of the current PU is defined as A₀, A₁, andscaled A₀, scaled A₁. The order of derivation for the above side of thecurrent PU is defined as B₀, B₁, B₂, scaled B₀, scaled B₁, scaled B₂.For each side there are therefore four cases that can be used as motionvector candidate, with two cases not required to use spatial scaling,and two cases where spatial scaling is used. The four different casesare summarized as follows:

-   -   No spatial scaling        -   (1) Same reference picture list, and same reference picture            index (same POC)        -   (2) Different reference picture list, but same reference            picture (same POC)    -   Spatial scaling        -   (3) Same reference picture list, but different reference            picture (different POC)        -   (4) Different reference picture list, and different            reference picture (different POC)

The no-spatial-scaling cases are checked first followed by the casesthat allow spatial scaling. Spatial scaling is considered when the POCis different between the reference picture of the neighbouring PU andthat of the current PU regardless of reference picture list. If all PUsof left candidates are not available or are intra coded, scaling for theabove motion vector is allowed to help parallel derivation of left andabove MV candidates. Otherwise, spatial scaling is not allowed for theabove motion vector.

As shown in the example in FIG. 9, for the spatial scaling case, themotion vector of the neighbouring PU is scaled in a similar manner asfor temporal scaling. One difference is that the reference picture listand index of current PU is given as input; the actual scaling process isthe same as that of temporal scaling.

1.2.3 Constructing Temporal Motion Vector Candidates

Apart from the reference picture index derivation, all processes for thederivation of temporal merge candidates are the same as for thederivation of spatial motion vector candidates (as shown in the examplein FIG. 6). In some embodiments, the reference picture index is signaledto the decoder.

2. Example of Inter Prediction Methods in Joint Exploration Model (JEM)

In some embodiments, future video coding technologies are explored usinga reference software known as the Joint Exploration Model (JEM) [3][4].In JEM, sub-block based prediction is adopted in several coding tools,such as affine prediction, alternative temporal motion vector prediction(ATMVP), spatial-temporal motion vector prediction (STMVP),bi-directional optical flow (BIO), Frame-Rate Up Conversion (FRUC),Locally Adaptive Motion Vector Resolution (LAMVR), Overlapped BlockMotion Compensation (OBMC), Local Illumination Compensation (LIC), andDecoder-side Motion Vector Refinement (DMVR).

2.1 Examples of Sub-CU Based Motion Vector Prediction

In the JEM with quadtrees plus binary trees (QTBT), each CU can have atmost one set of motion parameters for each prediction direction. In someembodiments, two sub-CU level motion vector prediction methods areconsidered in the encoder by splitting a large CU into sub-CUs andderiving motion information for all the sub-CUs of the large CU.Alternative temporal motion vector prediction (ATMVP) method allows eachCU to fetch multiple sets of motion information from multiple blockssmaller than the current CU in the collocated reference picture. Inspatial-temporal motion vector prediction (STMVP) method motion vectorsof the sub-CUs are derived recursively by using the temporal motionvector predictor and spatial neighbouring motion vector. In someembodiments, and to preserve more accurate motion field for sub-CUmotion prediction, the motion compression for the reference frames maybe disabled.

2.1.1 Examples of Alternative Temporal Motion Vector Prediction (ATMVP)

In the ATMVP method, the temporal motion vector prediction (TMVP) methodis modified by fetching multiple sets of motion information (includingmotion vectors and reference indices) from blocks smaller than thecurrent CU.

FIG. 10 shows an example of ATMVP motion prediction process for a CU1000. The ATMVP method predicts the motion vectors of the sub-CUs 1001within a CU 1000 in two steps. The first step is to identify thecorresponding block 1051 in a reference picture 1050 with a temporalvector. The reference picture 1050 is also referred to as the motionsource picture. The second step is to split the current CU 1000 intosub-CUs 1001 and obtain the motion vectors as well as the referenceindices of each sub-CU from the block corresponding to each sub-CU.

In the first step, a reference picture 1050 and the corresponding blockis determined by the motion information of the spatial neighboringblocks of the current CU 1000. To avoid the repetitive scanning processof neighboring blocks, the first merge candidate in the merge candidatelist of the current CU 1000 is used. The first available motion vectoras well as its associated reference index are set to be the temporalvector and the index to the motion source picture. This way, thecorresponding block may be more accurately identified, compared withTMVP, wherein the corresponding block (sometimes called collocatedblock) is always in a bottom-right or center position relative to thecurrent CU.

In the second step, a corresponding block of the sub-CU 1051 isidentified by the temporal vector in the motion source picture 1050, byadding to the coordinate of the current CU the temporal vector. For eachsub-CU, the motion information of its corresponding block (e.g., thesmallest motion grid that covers the center sample) is used to derivethe motion information for the sub-CU. After the motion information of acorresponding N×N block is identified, it is converted to the motionvectors and reference indices of the current sub-CU, in the same way asTMVP of HEVC, wherein motion scaling and other procedures apply. Forexample, the decoder checks whether the low-delay condition (e.g. thePOCs of all reference pictures of the current picture are smaller thanthe POC of the current picture) is fulfilled and possibly uses motionvector MVx (e.g., the motion vector corresponding to reference picturelist X) to predict motion vector MVy (e.g., with X being equal to 0 or 1and Y being equal to 1−X) for each sub-CU.

2.1.2 Examples of Spatial-Temporal Motion Vector Prediction (STMVP)

In the STMVP method, the motion vectors of the sub-CUs are derivedrecursively, following raster scan order. FIG. 11 shows an example ofone CU with four sub-blocks and neighboring blocks. Consider an 8×8 CU1100 that includes four 4×4 sub-CUs A (1101), B (1102), C (1103), and D(1104). The neighboring 4×4 blocks in the current frame are labelled asa (1111), b (1112), c (1113), and d (1114).

The motion derivation for sub-CU A starts by identifying its two spatialneighbors. The first neighbor is the N×N block above sub-CU A 1101(block c 1113). If this block c (1113) is not available or is intracoded the other N×N blocks above sub-CU A (1101) are checked (from leftto right, starting at block c 1113). The second neighbor is a block tothe left of the sub-CU A 1101 (block b 1112). If block b (1112) is notavailable or is intra coded other blocks to the left of sub-CU A 1101are checked (from top to bottom, staring at block b 1112). The motioninformation obtained from the neighboring blocks for each list is scaledto the first reference frame for a given list. Next, temporal motionvector predictor (TMVP) of sub-block A 1101 is derived by following thesame procedure of TMVP derivation as specified in HEVC. The motioninformation of the collocated block at block D 1104 is fetched andscaled accordingly. Finally, after retrieving and scaling the motioninformation, all available motion vectors are averaged separately foreach reference list. The averaged motion vector is assigned as themotion vector of the current sub-CU. 2.1.3 Examples of Sub-CU MotionPrediction Mode Signaling

In some embodiments, the sub-CU modes are enabled as additional mergecandidates and there is no additional syntax element required to signalthe modes. Two additional merge candidates are added to merge candidateslist of each CU to represent the ATMVP mode and STMVP mode. In otherembodiments, up to seven merge candidates may be used, if the sequenceparameter set indicates that ATMVP and STMVP are enabled. The encodinglogic of the additional merge candidates is the same as for the mergecandidates in the HM, which means, for each CU in P or B slice, two moreRD checks may be needed for the two additional merge candidates. In someembodiments, e.g., JEM, all bins of the merge index are context coded byCABAC (Context-based Adaptive Binary Arithmetic Coding). In otherembodiments, e.g., HEVC, only the first bin is context coded and theremaining bins are context by-pass coded.

2.2 Examples of Adaptive Motion Vector Difference Resolution

In some embodiments, motion vector differences (MVDs) (between themotion vector and predicted motion vector of a PU) are signalled inunits of quarter luma samples when use_integer_mv_flag is equal to 0 inthe slice header. In the JEM, a locally adaptive motion vectorresolution (LAMVR) is introduced. In the JEM, MVD can be coded in unitsof quarter luma samples, integer luma samples or four luma samples. TheMVD resolution is controlled at the coding unit (CU) level, and MVDresolution flags are conditionally signalled for each CU that has atleast one non-zero MVD components.

For a CU that has at least one non-zero MVD components, a first flag issignalled to indicate whether quarter luma sample MV precision is usedin the CU. When the first flag (equal to 1) indicates that quarter lumasample MV precision is not used, another flag is signalled to indicatewhether integer luma sample MV precision or four luma sample MVprecision is used.

When the first MVD resolution flag of a CU is zero, or not coded for aCU (meaning all MVDs in the CU are zero), the quarter luma sample MVresolution is used for the CU. When a CU uses integer-luma sample MVprecision or four-luma-sample MV precision, the MVPs in the AMVPcandidate list for the CU are rounded to the corresponding precision.

In the encoder, CU-level RD checks are used to determine which MVDresolution is to be used for a CU. That is, the CU-level RD check isperformed three times for each MVD resolution. To accelerate encoderspeed, the following encoding schemes are applied in the JEM:

-   -   During RD check of a CU with normal quarter luma sample MVD        resolution, the motion information of the current CU (integer        luma sample accuracy) is stored. The stored motion information        (after rounding) is used as the starting point for further small        range motion vector refinement during the RD check for the same        CU with integer luma sample and 4 luma sample MVD resolution so        that the time-consuming motion estimation process is not        duplicated three times.    -   RD check of a CU with 4 luma sample MVD resolution is        conditionally invoked. For a CU, when RD cost integer luma        sample MVD resolution is much larger than that of quarter luma        sample MVD resolution, the RD check of 4 luma sample MVD        resolution for the CU is skipped.

2.3 Examples of Higher Motion Vector Storage Accuracy

In HEVC, motion vector accuracy is one-quarter pel (one-quarter lumasample and one-eighth chroma sample for 4:2:0 video). In the JEM, theaccuracy for the internal motion vector storage and the merge candidateincreases to 1/16 pel. The higher motion vector accuracy ( 1/16 pel) isused in motion compensation inter prediction for the CU coded withskip/merge mode. For the CU coded with normal AMVP mode, either theinteger-pel or quarter-pel motion is used.

SHVC upsampling interpolation filters, which have same filter length andnormalization factor as HEVC motion compensation interpolation filters,are used as motion compensation interpolation filters for the additionalfractional pel positions. The chroma component motion vector accuracy is1/32 sample in the JEM, the additional interpolation filters of 1/32 pelfractional positions are derived by using the average of the filters ofthe two neighbouring 1/16 pel fractional positions.

2.4 Examples of Overlapped Block Motion Compensation (OBMC)

In the JEM, OBMC can be switched on and off using syntax at the CUlevel. When OBMC is used in the JEM, the OBMC is performed for allmotion compensation (MC) block boundaries except the right and bottomboundaries of a CU. Moreover, it is applied for both the luma and chromacomponents. In the JEM, an MC block corresponds to a coding block. Whena CU is coded with sub-CU mode (includes sub-CU merge, affine and FRUCmode), each sub-block of the CU is a MC block. To process CU boundariesin a uniform fashion, OBMC is performed at sub-block level for all MCblock boundaries, where sub-block size is set equal to 4×4, as shown inFIGS. 12A and 12B.

FIG. 12A shows sub-blocks at the CU/PU boundary, and the hatchedsub-blocks are where OBMC applies. Similarly, FIG. 12B shows the sub-Pusin ATMVP mode.

When OBMC applies to the current sub-block, besides current motionvectors, motion vectors of four connected neighboring sub-blocks, ifavailable and are not identical to the current motion vector, are alsoused to derive prediction block for the current sub-block. Thesemultiple prediction blocks based on multiple motion vectors are combinedto generate the final prediction signal of the current sub-block.

Prediction block based on motion vectors of a neighboring sub-block isdenoted as PN, with N indicating an index for the neighboring above,below, left and right sub-blocks and prediction block based on motionvectors of the current sub-block is denoted as PC. When PN is based onthe motion information of a neighboring sub-block that contains the samemotion information to the current sub-block, the OBMC is not performedfrom PN. Otherwise, every sample of PN is added to the same sample inPC, i.e., four rows/columns of PN are added to PC. The weighting factors{¼, ⅛, 1/16, 1/32} are used for PN and the weighting factors {¾, ⅞,15/16, 31/32} are used for PC. The exception are small MC blocks, (i.e.,when height or width of the coding block is equal to 4 or a CU is codedwith sub-CU mode), for which only two rows/columns of PN are added toPC. In this case weighting factors {¼, ⅛} are used for PN and weightingfactors {¾, ⅞} are used for PC. For PN generated based on motion vectorsof vertically (horizontally) neighboring sub-block, samples in the samerow (column) of PN are added to PC with a same weighting factor.

In the JEM, for a CU with size less than or equal to 256 luma samples, aCU level flag is signaled to indicate whether OBMC is applied or not forthe current CU. For the CUs with size larger than 256 luma samples ornot coded with AMVP mode, OBMC is applied by default. At the encoder,when OBMC is applied for a CU, its impact is taken into account duringthe motion estimation stage. The prediction signal formed by OBMC usingmotion information of the top neighboring block and the left neighboringblock is used to compensate the top and left boundaries of the originalsignal of the current CU, and then the normal motion estimation processis applied.

2.5 Examples of Local Illumination Compensation (LIC)

LIC is based on a linear model for illumination changes, using a scalingfactor a and an offset b. And it is enabled or disabled adaptively foreach inter-mode coded coding unit (CU).

When LIC applies for a CU, a least square error method is employed toderive the parameters a and b by using the neighboring samples of thecurrent CU and their corresponding reference samples. FIG. 13 shows anexample of neighboring samples used to derive parameters of the ICalgorithm. Specifically, and as shown in FIG. 13, the subsampled (2:1subsampling) neighbouring samples of the CU and the correspondingsamples (identified by motion information of the current CU or sub-CU)in the reference picture are used. The IC parameters are derived andapplied for each prediction direction separately.

When a CU is coded with merge mode, the LIC flag is copied fromneighboring blocks, in a way similar to motion information copy in mergemode; otherwise, an LIC flag is signaled for the CU to indicate whetherLIC applies or not.

When LIC is enabled for a picture, an additional CU level RD check isneeded to determine whether LIC is applied or not for a CU. When LIC isenabled for a CU, the mean-removed sum of absolute difference (MR-SAD)and mean-removed sum of absolute Hadamard-transformed difference(MR-SATD) are used, instead of SAD and SATD, for integer pel motionsearch and fractional pel motion search, respectively.

To reduce the encoding complexity, the following encoding scheme isapplied in the JEM:

-   -   LIC is disabled for the entire picture when there is no obvious        illumination change between a current picture and its reference        pictures. To identify this situation, histograms of a current        picture and every reference picture of the current picture are        calculated at the encoder. If the histogram difference between        the current picture and every reference picture of the current        picture is smaller than a given threshold, LIC is disabled for        the current picture; otherwise, LIC is enabled for the current        picture.

2.6 Examples of Affine Motion Compensation Prediction

In HEVC, only a translation motion model is applied for motioncompensation prediction (MCP). However, the camera and objects may havemany kinds of motion, e.g. zoom in/out, rotation, perspective motions,and/or other irregular motions. JEM, on the other hand, applies asimplified affine transform motion compensation prediction. FIG. 14shows an example of an affine motion field of a block 1400 described bytwo control point motion vectors V₀ and V₁. The motion vector field(MVF) of the block 1400 can be described by the following equation:

$\begin{matrix}\left\{ \begin{matrix}{v_{x} = {{\frac{\left( {v_{1x} - v_{0x}} \right)}{w}x} - {\frac{\left( {v_{1y} - v_{0y}} \right)}{w}y} + v_{0x}}} \\{v_{y} = {{\frac{\left( {v_{1y} - v_{0y}} \right)}{w}x} + {\frac{\left( {v_{1x} - v_{0x}} \right)}{w}y} + v_{0y}}}\end{matrix} \right. & {{Eq}.(1)}\end{matrix}$

As shown in FIG. 14, (v_(0x), v_(0y)) is motion vector of the top-leftcorner control point, and (v_(1x), v_(1y)) is motion vector of thetop-right corner control point. To simplify the motion compensationprediction, sub-block based affine transform prediction can be applied.The sub-block size M×N is derived as follows:

$\begin{matrix}\left\{ \begin{matrix}{M = {clip\ 3\ \left( {4,w,\ \frac{w \times {MvPre}}{\max\left( {{{abs}\left( {v_{1x} - v_{0x}} \right)},{{abs}\left( {v_{1y} - v_{0y}} \right)}} \right)}} \right)}} \\{N = {clip\ 3\ \left( {4,h,\ \frac{h \times {MvPre}}{\max\left( {{{abs}\left( {v_{2x} - v_{0x}} \right)},{{abs}\left( {v_{2y} - v_{0y}} \right)}} \right)}} \right)}}\end{matrix} \right. & {{Eq}.(2)}\end{matrix}$

Here, MvPre is the motion vector fraction accuracy (e.g., 1/16 in JEM).(v_(2x), v_(2y)) is motion vector of the bottom-left control point,calculated according to Eq. (1). M and N can be adjusted downward ifnecessary to make it a divisor of w and h, respectively.

FIG. 15 shows an example of affine MVF per sub-block for a block 1500.To derive motion vector of each M×N sub-block, the motion vector of thecenter sample of each sub-block can be calculated according to Eq. (1),and rounded to the motion vector fraction accuracy (e.g., 1/16 in JEM).Then the motion compensation interpolation filters can be applied togenerate the prediction of each sub-block with derived motion vector.After the MCP, the high accuracy motion vector of each sub-block isrounded and saved as the same accuracy as the normal motion vector.

2.6.1 Embodiments of the AF_INTER Mode

In the JEM, there are two affine motion modes: AF_INTER mode andAF_MERGE mode. For CUs with both width and height larger than 8,AF_INTER mode can be applied. An affine flag in CU level is signaled inthe bitstream to indicate whether AF_INTER mode is used. In the AF_INTERmode, a candidate list with motion vector pair {(v₀, v₁)|v₀={v_(A),v_(B), v_(c)}, v₁={v_(D),v_(E)}} is constructed using the neighboringblocks.

FIG. 16 shows an example of motion vector prediction (MVP) for a block1600 in the AF_INTER mode. As shown in FIG. 16, v₀ is selected from themotion vectors of the sub-block A, B, or C. The motion vectors from theneighboring blocks can be scaled according to the reference list. Themotion vectors can also be scaled according to the relationship amongthe Picture Order Count (POC) of the reference for the neighboringblock, the POC of the reference for the current CU, and the POC of thecurrent CU. The approach to select v₁ from the neighboring sub-block Dand E is similar. If the number of candidate list is smaller than 2, thelist is padded by the motion vector pair composed by duplicating each ofthe AMVP candidates. When the candidate list is larger than 2, thecandidates can be firstly sorted according to the neighboring motionvectors (e.g., based on the similarity of the two motion vectors in apair candidate). In some implementations, the first two candidates arekept. In some embodiments, a Rate Distortion (RD) cost check is used todetermine which motion vector pair candidate is selected as the controlpoint motion vector prediction (CPMVP) of the current CU. An indexindicating the position of the CPMVP in the candidate list can besignaled in the bitstream. After the CPMVP of the current affine CU isdetermined, affine motion estimation is applied and the control pointmotion vector (CPMV) is found. Then the difference of the CPMV and theCPMVP is signaled in the bitstream.

In AF_INTER mode, when 4/6 parameter affine mode is used, ⅔ controlpoints are required, and therefore ⅔ MVD needs to be coded for thesecontrol points, as shown in FIG. 17. In an existing implementation [5],the MV may be derived as follows, e.g., it predicts mvd₁ and mvd₂ frommvd₀.

mv ₀ =mv ₀ +mvd ₀

mv ₁ =mv ₁ +mvd ₁ +mvd ₀

mv ₂ =mv ₂ +mvd ₂ +mvd ₀

Herein, mv _(i), mvd_(i) and mv₁ are the predicted motion vector, motionvector difference and motion vector of the top-left pixel (i=0),top-right pixel (i=1) or left-bottom pixel (i=2) respectively, as shownin FIG. 18B. In some embodiments, the addition of two motion vectors(e.g., mvA(xA, yA) and mvB(xB, yB)) is equal to summation of twocomponents separately. For example, newMV=mvA+mvB implies that the twocomponents of newMV are set to (xA+xB) and (yA+yB), respectively.

2.6.2 Examples of Fast Affine ME Algorithms in AF_INTER Mode

In some embodiments of the affine mode, MV of 2 or 3 control pointsneeds to be determined jointly. Directly searching the multiple MVsjointly is computationally complex. In an example, a fast affine MEalgorithm [6] is proposed and is adopted into VTM/BMS.

For example, the fast affine ME algorithm is described for the4-parameter affine model, and the idea can be extended to 6-parameteraffine model:

$\begin{matrix}\left\{ \begin{matrix}{x^{\prime} = {{ax} + {by} + c}} \\{y^{\prime} = {{- {bx}} + {ay} + d}}\end{matrix} \right. & {{Eq}.(3)}\end{matrix}$ $\begin{matrix}\left\{ \begin{matrix}{{mv_{({x,y})}^{h}} = {{x^{\prime} - x} = {{\left( {a - 1} \right)x} + {by} + c}}} \\{{mv_{({x,y})}^{v}} = {{y^{\prime} - y} = {{{- b}x} + {\left( {a - 1} \right)y} + d}}}\end{matrix} \right. & {{Eq}.(4)}\end{matrix}$

Replacing (a−1) with a′ enables the motion vectors to be rewritten as:

$\begin{matrix}\left\{ \begin{matrix}{{mv_{({x,y})}^{h}} = {{x^{\prime} - x} = {{a^{\prime}x} + {by} + c}}} \\{{mv_{({x,y})}^{v}} = {{y^{\prime} - y} = {{{- b}x} + {a^{\prime}y} + d}}}\end{matrix} \right. & {{Eq}.(5)}\end{matrix}$

If it is assumed that the motion vectors of the two controls points (0,0) and (0, w) are known, from Equation (5) the affine parameters may bederived as:

$\begin{matrix}{\left\{ \begin{matrix}{c = {mv_{({0,0})}^{h}}} \\{d = {mv_{({0,0})}^{v}}}\end{matrix} \right..} & {{Eq}.(6)}\end{matrix}$

The motion vectors can be rewritten in vector form as:

MV(p)=A(P)*MV _(C) ^(T).  Eq. (7)

Herein, P=(x, y) is the pixel position,

$\begin{matrix}{{{A(P)} = \begin{bmatrix}1 & x & 0 & y \\0 & y & 1 & {- x}\end{bmatrix}},{and}} & {{Eq}.(8)}\end{matrix}$ $\begin{matrix}{{MV}_{C} = {\begin{bmatrix}{mv_{({0,0})}^{h}} & a & {mv}_{({0,0})}^{v} & b\end{bmatrix}.}} & {{Eq}.(9)}\end{matrix}$

In some embodiments, and at the encoder, the MVD of AF_INTER may bederived iteratively. Denote MV^(i)(P) as the MV derived in the ithiteration for position P and denote dMV_(C) ^(i) as the delta updatedfor MV_(C) in the ith iteration. Then in the (i+1)th iteration,

$\begin{matrix}\begin{matrix}{{{MV}^{i + 1}(P)} = {{A(P)}*\left( {\left( {MV_{C}^{i}} \right)^{T} + \left( {dMV_{C}^{i}} \right)^{T}} \right)}} \\{= {{{A(P)}*\left( {MV_{C}^{i}} \right)^{T}} + {{A(P)}*\left( {dMV_{C}^{i}} \right)^{T}}}} \\{= {{M{V^{i}(P)}} + {{A(P)}*{\left( {dMV_{C}^{i}} \right)^{T}.}}}}\end{matrix} & {{Eq}.(10)}\end{matrix}$

Denote Pic_(ref) as the reference picture and denote Pic_(cur) as thecurrent picture and denote Q=P+MV^(i)(P). If the MSE is used as thematching criterion, then the function that needs to be minimized may bewritten as:

$\begin{matrix}{{\min{\sum_{P}\left( {{Pi{c_{cur}(P)}} - {Pi{c_{ref}\left( {P + {M{V^{i + 1}(P)}}} \right)}}} \right)^{2}}} = {\min{\sum_{P}\left( {{Pi{c_{cur}(P)}} - {Pi{c_{ref}\left( {Q + {{A(P)}*\left( {dMV_{C}^{i}} \right)^{T}}} \right)}}} \right)^{2}}}} & {{Eq}.(11)}\end{matrix}$

If it is assumed that (dMV_(C) ^(i))^(T) is small enough, Pic_(ref)(Q+A(P)*(dMV_(C) ^(i))^(T)) may be rewritten, as an approximation basedon a 1-st order Taylor expansion, as:

Pic _(ref)(Q+A(P)*(dMV _(C) ^(i))^(T))≈Pic _(ref)(Q)+Pic_(ref)′(Q)*A(P)*(dMV _(C) ^(i))^(T).  (12)

Herein,

${{Pic}_{ref}^{\prime}(Q)} = {\left\lbrack {\frac{dPi{c_{ref}(Q)}}{dx}\frac{dPi{c_{ref}(Q)}}{dy}} \right\rbrack.}$

If the notation E^(i+1)(P)=Pic_(cur)(P)−Pic_(ref)(Q) is adopted, then:

$\begin{matrix}{{\min{\sum_{P}\left( {{Pi{c_{cur}(P)}} - {Pi{c_{ref}(Q)}} - {{{Pic}_{ref}^{\prime}(Q)}*{A(P)}*\left( {dMV_{C}^{i}} \right)^{T}}} \right)^{2}}} = {\min{\sum_{P}\left( {{E^{i + 1}(P)} - {{{Pic}_{ref}^{\prime}(Q)}*{A(P)}*\left( {dMV_{C}^{i}} \right)^{T}}} \right)^{2}}}} & {{Eq}.(13)}\end{matrix}$

The term dMV_(C) ^(i) may be derived by setting the derivative of theerror function to zero, and then computing delta MV of the controlpoints (0, 0) and (0, w) according to A(P)*(dMV_(C) ^(i))^(T), asfollows:

dMV _((0,0)) ^(h) =dMV _(C) ^(i)[0]  Eq. (14)

dMV _((0,w)) ^(h) =dMV _(C) ^(i)[1]*w+dMV _(C) ^(i)[2]  Eq. (15)

dMV _((0,0)) ^(v) =dMV _(C) ^(i)[2]  Eq. (16)

dMV _((0,w)) ^(v) =dMV _(C) ^(i)[3]*w+dMV _(C) ^(i)[2]  Eq. (17)

In some embodiments, this MVD derivation process may be iterated ntimes, and the final MVD may be calculated as follows:

fdMV _((0,0)) ^(h)=Σ_(i=0) ^(n−1) dMV _(C) ^(i)[0]  Eq. (18)

fdMV _((0,w)) ^(h)=Σ_(i=0) ^(n−1) dMV _(C) ^(i)[1]*w+Σ _(i=0) ^(n−1) dMV_(C) ^(i)[0]  Eq. (19)

fdMV _((0,0)) ^(v)=Σ_(i=0) ^(n−1) dMV _(C) ^(i)[2]  Eq. (20)

fdMV _((0,w)) ^(v)=Σ_(i=0) ^(n−1) dMV _(C) ^(i)[3]*w+Σ _(i=0) ^(n−1) dMV_(C) ^(i)[2]  Eq. (21)

In the aforementioned implementation [5], predicting delta MV of controlpoint (0, w), denoted by mvd₁ from delta MV of control point (0, 0),denoted by mvd₀, results in only Σ_(i=0) ^(n−1)dMV_(C) ^(i)[1]*w,−Σ_(i=0) ^(n−1)dMV_(C) ^(i)[3]*w) being encoded for mvd₁.

2.6.3 Embodiments of the AF_MERGE Mode

When a CU is applied in AF_MERGE mode, it gets the first block codedwith an affine mode from the valid neighboring reconstructed blocks.FIG. 18A shows an example of the selection order of candidate blocks fora current CU 1800. As shown in FIG. 18A, the selection order can be fromleft (1801), above (1802), above right (1803), left bottom (1804) toabove left (1805) of the current CU 1800. FIG. 18B shows another exampleof candidate blocks for a current CU 1800 in the AF_MERGE mode. If theneighboring left bottom block 1801 is coded in affine mode, as shown inFIG. 18B, the motion vectors v₂, v₃ and v₄ of the top left corner, aboveright corner, and left bottom corner of the CU containing the sub-block1801 are derived. The motion vector v₀ of the top left corner on thecurrent CU 1800 is calculated based on v₂, v₃ and v₄. The motion vectorv₁ of the above right of the current CU can be calculated accordingly.

After the CPMV of the current CU v₀ and v₁ are computed according to theaffine motion model in Eq. (1), the MVF of the current CU can begenerated. In order to identify whether the current CU is coded withAF_MERGE mode, an affine flag can be signaled in the bitstream whenthere is at least one neighboring block is coded in affine mode.

2.7 Examples of Pattern Matched Motion Vector Derivation (PMMVD)

The PMMVD mode is a special merge mode based on the Frame-Rate UpConversion (FRUC) method. With this mode, motion information of a blockis not signaled but derived at decoder side.

A FRUC flag can be signaled for a CU when its merge flag is true. Whenthe FRUC flag is false, a merge index can be signaled and the regularmerge mode is used. When the FRUC flag is true, an additional FRUC modeflag can be signaled to indicate which method (e.g., bilateral matchingor template matching) is to be used to derive motion information for theblock.

At the encoder side, the decision on whether using FRUC merge mode for aCU is based on RD cost selection as done for normal merge candidate. Forexample, multiple matching modes (e.g., bilateral matching and templatematching) are checked for a CU by using RD cost selection. The oneleading to the minimal cost is further compared to other CU modes. If aFRUC matching mode is the most efficient one, FRUC flag is set to truefor the CU and the related matching mode is used.

Typically, motion derivation process in FRUC merge mode has two steps: aCU-level motion search is first performed, then followed by a Sub-CUlevel motion refinement. At CU level, an initial motion vector isderived for the whole CU based on bilateral matching or templatematching. First, a list of MV candidates is generated and the candidatethat leads to the minimum matching cost is selected as the startingpoint for further CU level refinement. Then a local search based onbilateral matching or template matching around the starting point isperformed. The MV results in the minimum matching cost is taken as theMV for the whole CU. Subsequently, the motion information is furtherrefined at sub-CU level with the derived CU motion vectors as thestarting points.

For example, the following derivation process is performed for a W×H CUmotion information derivation. At the first stage, MV for the whole W×HCU is derived. At the second stage, the CU is further split into M×Msub-CUs. The value of M is calculated as in Eq. (3), D is a predefinedsplitting depth which is set to 3 by default in the JEM. Then the MV foreach sub-CU is derived.

$\begin{matrix}{M = {\max\left\{ {4,{\min\left\{ {\frac{M}{2^{D}},\frac{N}{2^{D}}} \right\}}} \right\}}} & {{Eq}.(3)}\end{matrix}$

FIG. 19 shows an example of bilateral matching used in the Frame-Rate UpConversion (FRUC) method. The bilateral matching is used to derivemotion information of the current CU by finding the closest matchbetween two blocks along the motion trajectory of the current CU (1900)in two different reference pictures (1910, 1911). Under the assumptionof continuous motion trajectory, the motion vectors MV0 (1901) and MV1(1902) pointing to the two reference blocks are proportional to thetemporal distances, e.g., TD0 (1903) and TD1 (1904), between the currentpicture and the two reference pictures. In some embodiments, when thecurrent picture 1900 is temporally between the two reference pictures(1910, 1911) and the temporal distance from the current picture to thetwo reference pictures is the same, the bilateral matching becomesmirror based bi-directional MV.

FIG. 20 shows an example of template matching used in the Frame-Rate UpConversion (FRUC) method. Template matching can be used to derive motioninformation of the current CU 2000 by finding the closest match betweena template (e.g., top and/or left neighboring blocks of the current CU)in the current picture and a block (e.g., same size to the template) ina reference picture 2010. Except the aforementioned FRUC merge mode, thetemplate matching can also be applied to AMVP mode. In both JEM andHEVC, AMVP has two candidates. With the template matching method, a newcandidate can be derived. If the newly derived candidate by templatematching is different to the first existing AMVP candidate, it isinserted at the very beginning of the AMVP candidate list and then thelist size is set to two (e.g., by removing the second existing AMVPcandidate). When applied to AMVP mode, only CU level search is applied.

The MV candidate set at CU level can include the following: (1) originalAMVP candidates if the current CU is in AMVP mode, (2) all mergecandidates, (3) several MVs in the interpolated MV field (describedlater), and top and left neighboring motion vectors.

When using bilateral matching, each valid MV of a merge candidate can beused as an input to generate a MV pair with the assumption of bilateralmatching. For example, one valid MV of a merge candidate is (MVa,ref_(a)) at reference list A. Then the reference picture ref_(b) of itspaired bilateral MV is found in the other reference list B so thatref_(a) and ref_(b) are temporally at different sides of the currentpicture. If such a ref_(b) is not available in reference list B, ref_(b)is determined as a reference which is different from ref_(a) and itstemporal distance to the current picture is the minimal one in list B.After ref_(b) is determined, MVb is derived by scaling MVa based on thetemporal distance between the current picture and ref_(a), ref_(b).

In some implementations, four MVs from the interpolated MV field canalso be added to the CU level candidate list. More specifically, theinterpolated MVs at the position (0, 0), (W/2, 0), (0, H/2) and (W/2,H/2) of the current CU are added. When FRUC is applied in AMVP mode, theoriginal AMVP candidates are also added to CU level MV candidate set. Insome implementations, at the CU level, 15 MVs for AMVP CUs and 13 MVsfor merge CUs can be added to the candidate list.

The MV candidate set at sub-CU level includes an MV determined from aCU-level search, (2) top, left, top-left and top-right neighboring MVs,(3) scaled versions of collocated MVs from reference pictures, (4) oneor more ATMVP candidates (e.g., up to four), and (5) one or more STMVPcandidates (e.g., up to four). The scaled MVs from reference picturesare derived as follows. The reference pictures in both lists aretraversed. The MVs at a collocated position of the sub-CU in a referencepicture are scaled to the reference of the starting CU-level MV. ATMVPand STMVP candidates can be the four first ones. At the sub-CU level,one or more MVs (e.g., up to 17) are added to the candidate list.

Generation of an interpolated MV field. Before coding a frame,interpolated motion field is generated for the whole picture based onunilateral ME. Then the motion field may be used later as CU level orsub-CU level MV candidates.

In some embodiments, the motion field of each reference pictures in bothreference lists is traversed at 4×4 block level. FIG. 21 shows anexample of unilateral Motion Estimation (ME) 2100 in the FRUC method.For each 4×4 block, if the motion associated to the block passingthrough a 4×4 block in the current picture and the block has not beenassigned any interpolated motion, the motion of the reference block isscaled to the current picture according to the temporal distance TD0 andTD1 (the same way as that of MV scaling of TMVP in HEVC) and the scaledmotion is assigned to the block in the current frame. If no scaled MV isassigned to a 4×4 block, the block's motion is marked as unavailable inthe interpolated motion field.

Interpolation and matching cost. When a motion vector points to afractional sample position, motion compensated interpolation is needed.To reduce complexity, bi-linear interpolation instead of regular 8-tapHEVC interpolation can be used for both bilateral matching and templatematching.

The calculation of matching cost is a bit different at different steps.When selecting the candidate from the candidate set at the CU level, thematching cost can be the absolute sum difference (SAD) of bilateralmatching or template matching. After the starting MV is determined, thematching cost C of bilateral matching at sub-CU level search iscalculated as follows:

C=SAD+w·(|MV _(x) −MV _(x) ^(s) |+|MV _(y) −MV _(y) ^(s)|)  Eq. (4)

Here, w is a weighting factor. In some embodiments, w can be empiricallyset to 4. MV and MV^(s) indicate the current MV and the starting MV,respectively. SAD may still be used as the matching cost of templatematching at sub-CU level search.

In FRUC mode, MV is derived by using luma samples only. The derivedmotion will be used for both luma and chroma for MC inter prediction.After MV is decided, final MC is performed using 8-taps interpolationfilter for luma and 4-taps interpolation filter for chroma.

MV refinement is a pattern based MV search with the criterion ofbilateral matching cost or template matching cost. In the JEM, twosearch patterns are supported—an unrestricted center-biased diamondsearch (UCBDS) and an adaptive cross search for MV refinement at the CUlevel and sub-CU level, respectively. For both CU and sub-CU level MVrefinement, the MV is directly searched at quarter luma sample MVaccuracy, and this is followed by one-eighth luma sample MV refinement.The search range of MV refinement for the CU and sub-CU step are setequal to 8 luma samples.

In the bilateral matching merge mode, bi-prediction is applied becausethe motion information of a CU is derived based on the closest matchbetween two blocks along the motion trajectory of the current CU in twodifferent reference pictures. In the template matching merge mode, theencoder can choose among uni-prediction from list0, uni-prediction fromlist1, or bi-prediction for a CU. The selection ca be based on atemplate matching cost as follows:

If costBi<=factor*min (cost0, cost1)

-   -   bi-prediction is used;

Otherwise, if cost0<=cost1

-   -   uni-prediction from list0 is used;

Otherwise,

-   -   uni-prediction from list1 is used;

Here, cost0 is the SAD of list0 template matching, cost1 is the SAD oflist1 template matching and costBi is the SAD of bi-prediction templatematching. For example, when the value of factor is equal to 1.25, itmeans that the selection process is biased toward bi-prediction. Theinter prediction direction selection can be applied to the CU-leveltemplate matching process.

2.8 Examples of Bi-Directional Optical Flow (BIO)

The bi-directional optical flow (BIO) method is a sample-wise motionrefinement performed on top of block-wise motion compensation forbi-prediction. In some implementations, the sample-level motionrefinement does not use signaling.

Let I^((k)) be the luma value from reference k (k=0, 1) after blockmotion compensation, and denote ∂I^((k))/∂x and ∂I^((k))/∂y as thehorizontal and vertical components of the I^((k)) gradient,respectively. Assuming the optical flow is valid, the motion vectorfield (v_(x), v_(y)) is given by:

∂I ^((k)) /∂t+v _(x) ∂I ^((k)) /∂x+v _(y) ∂I ^((k)) /∂y=0.  Eq. (5)

Combining this optical flow equation with Hermite interpolation for themotion trajectory of each sample results in a unique third-orderpolynomial that matches both the function values I^((k)) and derivatives∂I^((k))/∂x and ∂I^((k))/∂y at the ends. The value of this polynomial att=0 is the BIO prediction:

pred_(BIO)=½·(I ⁽⁰⁾ +I ⁽¹⁾ +v _(x)/2·(τ₁ ∂I ⁽¹⁾ /∂x−τ ₀ ∂I ⁽⁰⁾ /∂x)+v_(y)/2·(τ₁ ∂I ⁽¹⁾ /∂y−τ ₀ ∂I ⁽⁰⁾ /∂y)).  Eq. (6)

FIG. 22 shows an example optical flow trajectory in the B₁-directionalOptical flow (BIO) method. Here, τ₀ and τ₁ denote the distances to thereference frames. Distances τ₀ and τ₁ are calculated based on POC forRef₀ and Ref₁: τ₀=POC(current)−POC(Ref₀), τ₁=POC(Ref₁)−POC(current). Ifboth predictions come from the same time direction (either both from thepast or both from the future) then the signs are different (e.g.,τ₀·τ₁<0). In this case, BIO is applied if the prediction is not from thesame time moment (e.g., τ₀≠τ₁). Both referenced regions have non-zeromotion (e.g. MVx₀, MVy₀, MVx₁, MVy₁≠0), and the block motion vectors areproportional to the time distance (e.g., MVx₀/MVx₁=MVy₀/MVy₁=−τ₀/τ₁).

The motion vector field (v_(x), v_(y)) is determined by minimizing thedifference A between values in points A and B. FIGS. 9A-9B show anexample of intersection of motion trajectory and reference frame planes.Model uses only first linear term of a local Taylor expansion for Δ:

Δ=(I ⁽⁰⁾ −I ⁽¹⁾ ₀ +v _(x)(τ₁ ∂I ⁽¹⁾ /∂x+τ ₀ ∂I ⁽⁰⁾ /∂x)+v _(y)(τ₁ ∂I ⁽¹⁾/∂y+τ ₀ ∂I ⁽⁰⁾ /∂y)).  Eq. (7)

All values in the above equation depend on the sample location, denotedas (i′, j′). Assuming the motion is consistent in the local surroundingarea, A can be minimized inside the (2M+1)×(2M+1) square window Ωcentered on the currently predicted point (i,j), where M is equal to 2:

$\begin{matrix}{\left( {v_{x},v_{y}} \right) = {\underset{v_{x},v_{y}}{\arg\min}{\sum\limits_{{\lbrack{i^{\prime},j}\rbrack} \in \Omega}{\Delta^{2}\left\lbrack {i^{\prime},j^{\prime}} \right\rbrack}}}} & {{Eq}.(8)}\end{matrix}$

For this optimization problem, the JEM uses a simplified approach makingfirst a minimization in the vertical direction and then in thehorizontal direction. This results in the following:

$\begin{matrix}{v_{x} = {\left( {s_{1} + r} \right) > {{m?{clip}}3\left( {{- {thBIO}},{thBIO},{- \frac{s_{3}}{\left( {s_{1} + r} \right)}}} \right):0}}} & {{Eq}.(9)}\end{matrix}$ $\begin{matrix}{v_{y} = {\left( {s_{5} + r} \right) > {{m?{clip}}3\left( {{- {thBIO}},{thBIO},{- \frac{s_{6} - {v_{x}{s_{2}/2}}}{\left( {s_{5} + r} \right)}}} \right):0}}} & {{Eq}.(10)}\end{matrix}$ where, $\begin{matrix}{{{s_{1} = {\sum\limits_{{\lbrack{i^{\prime},j}\rbrack} \in \Omega}\left( {{\tau_{1}{{\partial I^{(1)}}/{\partial x}}} + {\tau_{0}{\partial I^{{(0)}/\partial_{X}}}}} \right)^{2}}};}{{s_{3} = {\sum\limits_{{\lbrack{i^{\prime},j}\rbrack} \in \Omega}{\left( {I^{(1)} - I^{(0)}} \right)\left( {{\tau_{1}{{\partial I^{(1)}}/{\partial x}}} + {\tau_{0}{{\partial I^{(0)}}/{\partial x}}}} \right)}}};}} & {{Eq}.(11)}\end{matrix}$${s_{2} = {\sum\limits_{{\lbrack{i^{\prime},j}\rbrack} \in \Omega}{\left( {{\tau_{1}{{\partial I^{(1)}}/{\partial x}}} + {\tau_{0}{{\partial I^{(0)}}/\partial_{x}}}} \right)\left( {{\tau_{1}{{\partial I^{(1)}}/{\partial y}}} + {\tau_{0}{{\partial I^{(0)}}/{\partial y}}}} \right)}}};$${s_{5} = {\sum\limits_{{\lbrack{i^{\prime},j}\rbrack} \in \Omega}\left( {{\tau_{1}{{\partial I^{(1)}}/{\partial y}}} + {\tau_{0}{{\partial I^{(0)}}/{\partial y}}}} \right)^{2}}};$$s_{6} = {\sum\limits_{{\lbrack{i^{\prime},j}\rbrack} \in \Omega}{\left( {I^{(1)} - I^{(0)}} \right)\left( {{\tau_{1}{{\partial I^{(1)}}/{\partial y}}} + {\tau_{0}{{\partial I^{(0)}}/{\partial y}}}} \right)}}$

In order to avoid division by zero or a very small value, regularizationparameters r and m can be introduced in Eq. (9) and Eq. (10), where:

r=500·4^(d−8) Eq. (12)

m=700·4^(d−8) Eq. (13)

Here, d is bit depth of the video samples.

In order to keep the memory access for BIO the same as for regularbi-predictive motion compensation, all prediction and gradients values,I^((k)), ∂I^((k))/∂x, ∂I^((k))/∂_(y), are calculated for positionsinside the current block. FIG. 23A shows an example of access positionsoutside of a block 2300. As shown in FIG. 23A, in Eq. (9), (2M+1)×(2M+1)square window Ω centered in currently predicted point on a boundary ofpredicted block needs to accesses positions outside of the block. In theJEM, values of I^((k)), ∂I^((k))/∂x, ∂I^((k))/∂y outside of the blockare set to be equal to the nearest available value inside the block. Forexample, this can be implemented as a padding area 2301, as shown inFIG. 23B.

With BIO, it is possible that the motion field can be refined for eachsample. To reduce the computational complexity, a block-based design ofBIO is used in the JEM. The motion refinement can be calculated based ona 4×4 block. In the block-based BIO, the values of s_(n) in Eq. (9) ofall samples in a 4×4 block can be aggregated, and then the aggregatedvalues of s_(n) in are used to derived BIO motion vectors offset for the4×4 block. More specifically, the following formula can used forblock-based BIO derivation:

$\begin{matrix}{{s_{1,b_{k}} = {\sum\limits_{{({x,y})} \in b_{k}}{\sum\limits_{{\lbrack{i^{\prime},j}\rbrack} \in {\Omega({x,y})}}\left( {{\tau_{1}{{\partial I^{(1)}}/{\partial x}}} + {\tau_{0}{{\partial I^{(0)}}/{\partial x}}}} \right)^{2}}}};} & {{Eq}.(14)}\end{matrix}$$s_{3,b_{k}} = {\sum\limits_{{({x,y})} \in b_{k}}{\sum\limits_{{\lbrack{i^{\prime},j}\rbrack} \in \Omega}\left( {{I^{(1)} - {I^{(0)}\left( {{\tau_{1}{{\partial I^{(1)}}/{\partial x}}} + {\tau_{0}{{\partial I^{(0)}}/{\partial x}}}} \right)}};} \right.}}$$\begin{matrix}{{s_{2,b_{k}} = {\sum\limits_{{({x,y})} \in b_{k}}{\sum\limits_{{\lbrack{i^{\prime},j}\rbrack} \in \Omega}{\left( {{\tau_{1}{{\partial I^{(1)}}/{\partial x}}} + {\tau_{0}{{\partial I^{(0)}}/{\partial x}}}} \right)\left( {{\tau_{1}{{\partial I^{(1)}}/{\partial y}}} + {\tau_{0}{{\partial I^{(0)}}/{\partial y}}}} \right)}}}};} & \end{matrix}$${s_{5,b_{k}} = {\sum\limits_{{({x,y})} \in b_{k}}{\sum\limits_{{\lbrack{i^{\prime},j}\rbrack} \in \Omega}\left( {{\tau_{1}{{\partial I^{(1)}}/{\partial y}}} + {\tau_{0}{{\partial I^{(0)}}/{\partial y}}}} \right)^{2}}}};$$s_{6,b_{k}} = {\sum\limits_{{({x,y})} \in b_{k}}{\sum\limits_{{\lbrack{i^{\prime},j}\rbrack} \in \Omega}{\left( {I^{(1)} - I^{(0)}} \right)\left( {{\tau_{1}{{\partial I^{(1)}}/{\partial y}}} + {\tau_{0}{{\partial I^{(0)}}/{\partial y}}}} \right)}}}$

Here, b_(k) denotes the set of samples belonging to the k-th 4×4 blockof the predicted block. s_(n) in Eq (9) and Eq (10) are replaced by((s_(n,bk))>>4) to derive the associated motion vector offsets.

In some scenarios, MV regiment of BIO may be unreliable due to noise orirregular motion. Therefore, in BIO, the magnitude of MV regiment isclipped to a threshold value. The threshold value is determined based onwhether the reference pictures of the current picture are all from onedirection. For example, if all the reference pictures of the currentpicture are from one direction, the value of the threshold is set to12×2^(14−d); otherwise, it is set to 12×2^(13−d).

Gradients for BIO can be calculated at the same time with motioncompensation interpolation using operations consistent with HEVC motioncompensation process (e.g., 2D separable Finite Impulse Response (FIR)).In some embodiments, the input for the 2D separable FIR is the samereference frame sample as for motion compensation process and fractionalposition (fracX,fracY) according to the fractional part of block motionvector. For horizontal gradient ∂I/∂x, a signal is first interpolatedvertically using BIOfilterS corresponding to the fractional positionfracY with de-scaling shift d−8. Gradient filter BIOfilterG is thenapplied in horizontal direction corresponding to the fractional positionfracX with de-scaling shift by 18−d. For vertical gradient ∂I/∂y, agradient filter is applied vertically using BIOfilterG corresponding tothe fractional position fracY with de-scaling shift d−8. The signaldisplacement is then performed using BIOfilterS in horizontal directioncorresponding to the fractional position fracX with de-scaling shift by18−d. The length of interpolation filter for gradients calculationBIOfilterG and signal displacement BIOfilterF can be shorter (e.g.,6-tap) in order to maintain reasonable complexity. Table 1 shows examplefilters that can be used for gradients calculation of differentfractional positions of block motion vector in BIO. Table 2 showsexample interpolation filters that can be used for prediction signalgeneration in BIO.

TABLE 1 Exemplary filters for gradient calculations in BIO Fractionalpel Interpolation filter for gradient position (BIOfilterG) 0 { 8, −39,−3, 46, −17, 5} 1/16 { 8, −32, −13, 50, −18, 5} 1/8  { 7, −27, −20, 54,−19, 5} 3/16 { 6, −21, −29, 57, −18, 5} 1/4  { 4, −17, −36, 60, −15, 4}5/16 { 3, −9, −44, 61, −15, 4} 3/8  { 1, −4, −48, 61, −13, 3} 7/16 { 0,1, −54, 60, −9, 2} 1/2  { −1, 4, −57, 57, −4, 1}

TABLE 2 Exemplary interpolation filters for prediction signal generationin BIO Fractional pel Interpolation filter for prediction positionsignal(BIOfilterS) 0 { 0, 0, 64, 0, 0, 0} 1/16 { 1, −3, 64, 4, −2, 0}1/8  { 1, −6, 62, 9, −3, 1} 3/16 { 2, −8, 60, 14, −5, 1} 1/4  { 2, −9,57, 19, −7, 2} 5/16 { 3, −10, 53, 24, −8, 2} 3/8  { 3, −11, 50, 29, −9,2} 7/16 { 3, −11, 44, 35, −10, 3} 1/2  { 3, −10, 35, 44, −11, 3}

In the JEM, BIO can be applied to all bi-predicted blocks when the twopredictions are from different reference pictures. When LocalIllumination Compensation (LIC) is enabled for a CU, BIO can bedisabled.

In some embodiments, OBMC is applied for a block after normal MCprocess. To reduce the computational complexity, BIO may not be appliedduring the OBMC process. This means that BIO is applied in the MCprocess for a block when using its own MV and is not applied in the MCprocess when the MV of a neighboring block is used during the OBMCprocess.

2.9 Examples of Decoder-Side Motion Vector Refinement (DMVR)

In a bi-prediction operation, for the prediction of one block region,two prediction blocks, formed using a motion vector (MV) of list0 and aMV of list1, respectively, are combined to form a single predictionsignal. In the decoder-side motion vector refinement (DMVR) method, thetwo motion vectors of the bi-prediction are further refined by abilateral template matching process. The bilateral template matchingapplied in the decoder to perform a distortion-based search between abilateral template and the reconstruction samples in the referencepictures in order to obtain a refined MV without transmission ofadditional motion information.

In DMVR, a bilateral template is generated as the weighted combination(i.e. average) of the two prediction blocks, from the initial MV0 oflist0 and MV1 of list1, respectively, as shown in FIG. 24. The templatematching operation consists of calculating cost measures between thegenerated template and the sample region (around the initial predictionblock) in the reference picture. For each of the two reference pictures,the MV that yields the minimum template cost is considered as theupdated MV of that list to replace the original one. In the JEM, nine MVcandidates are searched for each list. The nine MV candidates includethe original MV and 8 surrounding MVs with one luma sample offset to theoriginal MV in either the horizontal or vertical direction, or both.Finally, the two new MVs, i.e., MV0′ and MV1′ as shown in FIG. 24, areused for generating the final bi-prediction results. A sum of absolutedifferences (SAD) is used as the cost measure.

DMVR is applied for the merge mode of bi-prediction with one MV from areference picture in the past and another from a reference picture inthe future, without the transmission of additional syntax elements. Inthe JEM, when LIC, affine motion, FRUC, or sub-CU merge candidate isenabled for a CU, DMVR is not applied.

2.2.9 Examples of Symmetric Motion Vector Difference

In [8], symmetric motion vector difference (SMVD) is proposed to encodethe MVD more efficiently.

Firstly, in slice level, variables BiDirPredFlag, RefIdxSymL0 andRefIdxSymL1 are derived as follows:

The forward reference picture in reference picture list 0 which isnearest to the current picture is searched. If found, RefIdxSymL0 is setequal to the reference index of the forward picture.

The backward reference picture in reference picture list 1 which isnearest to the current picture is searched. If found, RefIdxSymL1 is setequal to the reference index of the backward picture.

If both forward and backward picture are found, BiDirPredFlag is setequal to 1.

Otherwise, following applies:

The backward reference picture in reference picture list 0 which isnearest to the current one is searched. If found, RefIdxSymL0 is setequal to the reference index of the backward picture.

The forward reference picture in reference picture list 1 which isnearest to the current one is searched. If found, RefIdxSymL1 is setequal to the reference index of the forward picture.

If both backward and forward picture are found, BiDirPredFlag is setequal to 1. Otherwise, BiDirPredFlag is set equal to 0.

Secondly, in CU level, a symmetrical mode flag indicating whethersymmetrical mode is used or not is explicitly signaled if the predictiondirection for the CU is bi-prediction and BiDirPredFlag is equal to 1.

When the flag is true, only mvp_l0_flag, mvp_l1_flag and MVD0 areexplicitly signaled. The reference indices are set equal to RefIdxSymL0,RefIdxSymL1 for list 0 and list 1, respectively. MVD1 is just set equalto −MVD0. The final motion vectors are shown in below formula.

$\left\{ \begin{matrix}{\left( {{mvx}_{0},{{mv}y_{0}}} \right) = \left( {{{mvpx_{0}} + {mvdx_{0}}},{{{mvp}y_{0}} + {mvdy_{0}}}} \right)} \\{\left( {{{mv}x_{1}},{{mv}y_{1}}} \right) = \left( {{{mvpx_{1}} - {mvdx_{0}}},{{{mvp}y_{1}} - {mvdy_{0}}}} \right)}\end{matrix} \right.$

FIG. 27 shows examples of symmetrical mode.

The modifications in coding unit syntax are shown in Table 3.

TABLE 3 Modifications in coding unit syntax Descriptor coding_unit( x0,y0, cbWidth, cbHeight, treeType ) { ...     if( slice_type = = B)     inter_pred_idc[ x0 ][ y0 ] ae(v)     if( sps_affine_enabled_flag &&cbWidth >= 16 && cbHeight >= 16 ) {      inter_affine_flag[ x0 ][ y0 ]ae(v)      if( sps_affine_type_flag && inter_affine_flag[ x0 ][ y0 ] )      cu_affine_type_flag[ x0 ][ y0 ] ae(v)     }     if(inter_pred_idc[ x0 ][ y0 ] == PRED_BI &&      BiDirPredFlag &&inter_affine_flag[ x0 ][ y0 ] == 0 )      symmetric_mvd_flag[ x0 ][ y0 ]ae(v)     if( inter_pred_idc[ x0 ][ y0 ] != PRED_L1 ) {      if( num_refidx_10_active_minus1 > 0 && !symmetric_mvd_flag[ x0 ][ y0 ] )      ref_idx_I0[ x0 ][ y0 ] ae(v)      mvd_coding( x0, y0, 0, 0 )     if( MotionModelIdc[ x0 ][ y0 ] > 0 )       mvd_coding( x0, y0, 0, 1)      if(MotionModelIdc[ x0 ][ y0 ] > 1 )       mvd_coding( x0, y0, 0,2 )      mvp_I0_flag[ x0 ][ y0 ] ae(v)     } else {      MvdL0[ x0 ][ y0][ 0 ] = 0      MvdL0[ x0 ][ y0 ][ 1 ] = 0     }     if( inter_pred_idc[x0 ][ y0 ] != PRED_L0 ) {      if( num_ref_idx_I1_active_minus1 >0 &&!symmetric_mvd_flag[ x0 ][ y0 ] )       ref idx_I1[ x0 ][ y0 ] ae(v)     if( mvd_I1_zero_flag && inter_pred_idc[ x0 ][ y0 ] = = PRED_BI ) {      ...      } else {       if( !symmetric_mvd_flag[ x0 ][ y0 ] ) {       mvd_coding( x0, y0, 1, 0 )       if( MotionModelIdc[ x0 ][ y0 ] >0 )        mvd_coding( x0, y0, 1, 1 )       if(MotionModelIdc[ x0 ][ y0] > 1 )        mvd_coding( x0, y0, 1, 2 )      }      mvp_I1_flag[ x0 ][y0 ] ae(v)     } else {      MvdL1[ x0 ][ y0 ][ 0 ] = 0      MvdL1[ x0][ y0 ][ 1 ] = 0     }     ...    }   }   ... }

2.2.11 Symmetric MVD for Affine Bi-Prediction Coding

SMVD for affine mode is proposed in [9].

2.3 Context-Adaptive Binary Arithmetic Coding (CABAC)

2.3.1 CABAC Design in HEVC

2.3.1.1 Context Representation and Initialization Process in HEVC

In HEVC, for each context variable, the two variables pStateIdx andvalMps are initialized.

From the 8 bit table entry initValue, the two 4 bit variables slopeIdxand offsetIdx are derived as follows:

slopeIdx=initValue>>4

offsetIdx=initValue & 15   (34)

The variables m and n, used in the initialization of context variables,are derived from slopeIdx and offsetIdx as follows:

m=slopeIdx*5−45

n=(offsetIdx<<3)−16   (35)

The two values assigned to pStateIdx and valMps for the initializationare derived from the luma's quantization parameter of slice denoted bySliceQpY. Given the variables m and n, the initialization is specifiedas follows:

preCtxState=Clip3(1,126,((m*Clip3(0,51,SliceQpY))>>4)+n)

valMps=(preCtxState<=63)?0:1

pStateIdx=valMps?(preCtxState−64):(63−preCtxState)  (36)

2.3.1.2 State Transition Process in HEVC

Inputs to this process are the current pStateIdx, the decoded valuebinVal and valMps values of the context variable associated withctxTable and ctxIdx.

Outputs of this process are the updated pStateIdx and valMps of thecontext variable associated with ctxIdx.

Depending on the decoded value binVal, the update of the two variablespStateIdx and valMps associated with ctxIdx is derived as follows in(37):

if( binVal = = valMps )   pStateIdx = transIdxMps( pStateIdx ) else {(37)  if( pStateIdx = = 0 ) valMps = 1 □ valMps  pStateIdx =transIdxLps( pStateIdx ) }

2.3.2 CABAC Design in VVC

The context-adaptive binary arithmetic coder (BAC) in VVC has beenchanged in VVC which is different from that in HEVC in terms of bothcontext updating process and arithmetic coder.

Here is the summary of recently adopted proposal (JVET-M0473, CE test5.1.13).

TABLE 4 Summary of CABAC modifications in VVC State representation 10 +14 bit linear, reduced range rLPS computation 5 × 4 bit multiplierInitialization 128 × 16 bit to map HEVC-like state to linearrepresentation, retrained initialization values Rate estimation 256 × 2× 19 bit table Window size Variable, defined per context (controllingprobability a = 2 . . . 5 b = a + 3 . . . 6 updating speed) That is,each context has two variables for recording the associatedprobabilities, and each probability is updated with its own speed(faster speed based on the variable a and lower speed based on thevariable b) Other rMPS >= 128 is guaranteed

2.3.2.1 Context Initialization Process in VVC

n VVC, two values assigned to pStateIdx0 and pStateIdx1 for theinitialization are derived from SliceQpY. Given the variables m and n,the initialization is specified as follows:

preCtxState=Clip3(0,127,((m*Clip3(0,51,SliceQpY))>>4)+n)

pStateIdx0=initStateIdxToState[preCtxState]>>4

pStateIdx1=initStateIdxToState[preCtxState]  (38)

2.3.2.2 State Transition Process in VVC

Inputs to this process are the current pStateIdx0 and pStateIdx1, andthe decoded value binVal.

Outputs of this process are the updated pStateIdx0 and pStateIdx1 of thecontext variable associated with ctxIdx.

The variables shift0 (corresponding to variable a in Summary of CABACmodifications in VVCTable 4) and shift1 (corresponding to variable b inSummary of CABAC modifications in VVC Table 4e) are derived from theshiftIdx value associated with ctxTable and ctxInc.

shift0=(shiftIdx>>2)+2

shift1=(shiftIdx & 3)+3+shift0  (39)

Depending on the decoded value binVal, the update of the two variablespStateIdx0 and pStateIdx1 associated with ctxIdx is derived as follows:

pStateIdx0=pStateIdx0−(pStateIdx0>>shift0)+(1023*binVal>>shift0)

pStateIdx1=pStateIdx1−(pStateIdx1>>shift1)+(16383*binVal>>shift1)  (40)

3. Drawbacks of Existing Implementations

In some existing implementations, when MV/MV difference (MVD) could beselected from a set of multiple MV/MVD precisions for affine codedblocks, it remains uncertain how more accurate motion vectors may beobtained.

In other existing implementations, the MV/MVD precision information alsoplays an important role in determination of the overall coding gain ofAMVR applied to affine mode, but achieving this goal remains uncertain.

4. Example Methods for MV Predictors for Affine Mode with AMVR

Embodiments of the presently disclosed technology overcome the drawbacksof existing implementations, thereby providing video coding with highercoding efficiencies. The derivation and signaling of motion vectorpredictors for affine mode with adaptive motion vector resolution(AMVR), based on the disclosed technology, may enhance both existing andfuture video coding standards, is elucidated in the following examplesdescribed for various implementations. The examples of the disclosedtechnology provided below explain general concepts, and are not meant tobe interpreted as limiting. In an example, unless explicitly indicatedto the contrary, the various features described in these examples may becombined.

In some embodiments, the following examples may be applied to affinemode or normal mode when AMVR is applied. These examples assume that aprecision Prec (i.e., MV is with 1/(2{circumflex over ( )}Prec)precision) is used for encoding MVD in AF_INTER mode or for encoding MVDin normal inter mode. A motion vector predictor (e.g., inherited from aneighboring block MV) and its precision are denoted byMVPred(MVPred_(X), MVPred_(Y)) and PredPrec, respectively.

In the following discussion, SatShift(x, n) is defined as

${{SatShift}\left( {x,n} \right)} = \left\{ \begin{matrix}{\left( {x + {{offsset}0}} \right) \gg {n\ {if}\ x} \geq 0} \\{{{- \left( {\left( {{- x} + {{offset}1}} \right) \gg n} \right)}\ {if}\ x} < 0}\end{matrix} \right.$

Shift(x, n) is defined as Shift(x, n)=(x+offset0)>>n. In one example,offset0 and/or offset1 are set to (1<<n)>>1 or (1<<(n−1)). In anotherexample, offset0 and/or offset1 are set to 0. In another example,offset0=offset1=((1<<n)>>1)−1 or ((1<<(n−1)))−1.

In the following discussion, an operation between two motion vectorsmeans the operation will be applied to both the two components of themotion vector. For example, MV3=MV1+MV2 is equivalent to MV3x=MV1x+MV2xand MV3y=MV1y+MV2y. alternatively, the operation may be only applied tothe horizontal or vertical component of the two motion vectors.

Example 1. It is proposed that final MV precision may be kept unchanged,i.e., same as the precision of motion vectors to be stored.

(a) In one example, the final MV precision may be set to 1/16-pel or⅛-pel.

(b) In one example, the signaled MVD may be firstly scaled and thenadded to the MVP to form the final MV for one block.

Example 2. The MVP directly derived from neighboring blocks (e.g.,spatial or temporal) or default MVPs may be firstly modified and thenadded to the signaled MVD to form the final MV for a (current) block.

(a) Alternatively, whether to apply and how to apply modifications ofMVP may be different for different values of Prec.

(b) In one example, if Prec is greater than 1 (i.e., MVD is withfractional precision), precision of the neighboring MV is not changedand the scaling is not performed.

(c) In one example, if Prec is equal to 1 (i.e., MVD is with 1-pelprecision), MV predictor (i.e., neighboring blocks' MV) need to bescaled, e.g., according to Example 4(b) of PCT ApplicationPCT/CN2018/104723.

(d) In one example, if Prec is smaller than 1 (i.e., MVD is with 4-pelprecision), MV predictor (i.e., neighboring blocks' MV) need to bescaled, e.g., according to Example 4(b) of PCT ApplicationPCT/CN2018/104723.

Example 3. In one example, if the precision of MVD signaled is the sameas the precision of stored MVs, no scaling is needed after the affineMVs are reconstructed, Otherwise, the MV is reconstructed with theprecision of the signaled MVD and then scaled to the precision of thestored MVs.

Example 4. In one example, normal inter mode and AF_INTER mode maychoose implementations based on the different examples described above.

Example 5. In one example, a syntax element to indicate the MV/MVDprecisions for affine mode may be signaled, with the followingsemantics:

(a) In one example, the syntax element equal to 0, 1 and 2 indicates¼-pel, 1/16-pel and 1-pel MV precision respectively.

(b) Alternatively, in affine mode, the syntax element equal to 0, 1 and2 indicates ¼-pel, 1-pel and 1/16-pel MV precision respectively.

(c) Alternatively, in affine mode, the syntax element equal to 0, 1 and2 indicates 1/16-pel, ¼-pel and 1-pel MV precision respectively.

Example 6. In one example, whether to enable or disable AMVR for affinemode may be signaled in SPS, PPS, VPS, sequence/picture/sliceheader/tile, etc. al.

Example 7. In one example, indications of allowed MV/MVD precisions maybe signaled in SPS, PPS, VPS, sequence/picture/slice header/tile, etc.

(a) Indications of selected MVD precision may be signaled for eachcoding tree unit (CTU) and/or each region.

(b) The set of allowed MV/MVD precisions may depend on the coded mode ofthe current block (e.g., affine or non-affine).

(c) The set of allowed MV/MVD precisions may depend on slicetype/temporal layer index/low delay check flag.

(d) The set of allowed MV/MVD precisions may depend on block size and/orblock shapes of the current or a neighboring block.

(e) The set of allowed MV/MVD precisions may depend on the precision ofMVs to be stored in decoded picture buffer.

(i) In one example, if the stored MV is in X-pel, the allowed MV/MVDprecision set may at least have X-pel.

Improvement of Affine Mode with AMVR Supported

Example 8. The set of allowed MVD precisions may be different frompicture to picture, from slice to slice, or from block to block.

-   -   a. In one example, the set of allowed MVD precisions may depend        on coded information, such as block size, block shape. etc. al.    -   b. A set of allowed MV precisions may be pre-defined, such as {        1/16, ¼, 1}.    -   c. Indications of allowed MV precisions may be signaled in        SPS/PPS/VPS/sequence header/picture header/slice header/group of        CTUs, etc. al.    -   d. The signaling of selected MV precision from a set of allowed        MV precisions further depend on number of allowed MV precisions        for a block.

Example 9. A syntax element is signaled to the decoder to indicate theused MVD precision in affine inter mode.

-   -   a. In one example, only one single syntax element is used to        indicate the MVD precisions applied to the affine mode and the        AMVR mode.        -   i. In one example, same semantics are used, that is, the            same value of syntax element is mapped to the same MVD            precision for the AMVR and affine mode.        -   ii. Alternatively, the semantics of the single syntax            element is different for the AMVR mode and the affine mode.            That is, the same value of syntax element could be mapped to            different MVD precision for the AMVR and affine mode.    -   b. In one example, when affine mode uses same set of MVD        precisions with AMVR (e.g., MVD precision set is {1, ¼, 4}-pel),        the MVD precision syntax element in AMVR is reused in affine        mode, i.e., only one single syntax element is used.        -   i. Alternatively, furthermore, when encoding/decoding this            syntax element in CABAC encoder/decoder, same or different            context models may be used for AMVR and affine mode.        -   ii. Alternatively, furthermore, this syntax element may have            different semantics in AMVR and affine mode. For example,            the syntax element equal to 0, 1 and 2 indicates ¼-pel,            1-pel and 4-pel MV precision respectively in AMVR, while in            affine mode, the syntax element equal to 0, 1 and 2            indicates ¼-pel, 1/16-pel and 1-pel MV precision            respectively.    -   c. In one example, when affine mode uses same number of MVD        precisions with AMVR but different sets of MVD precisions (e.g.,        MVD precision set for AMVR is {1, ¼, 4}-pel while for affine, it        is { 1/16, ¼, 1}-pel), the MVD precision syntax element in AMVR        is reused in affine mode, i.e., only one single syntax element        is used.        -   i. Alternatively, furthermore, when encoding/decoding this            syntax element in CABAC encoder/decoder, same or different            context models may be used for AMVR and affine mode.        -   ii. Alternatively, furthermore, this syntax element may have            different semantics in AMVR and affine mode.    -   d. In one example, affine mode uses less MVD precisions than        AMVR, the MVD precision syntax element in AMVR is reused in        affine mode. However, only a subset of the syntax element values        is valid for affine mode.        -   i. Alternatively, furthermore, when encoding/decoding this            syntax element in CABAC encoder/decoder, same or different            context models may be used for AMVR and affine mode.        -   ii. Alternatively, furthermore, this syntax element may have            different semantics in AMVR and affine mode.    -   e. In one example, affine mode uses more MVD precisions than        AMVR, the MVD precision syntax element in AMVR is reused in        affine mode. However, such syntax element is extended to allow        more values in affine mode.        -   i. Alternatively, furthermore, when encoding/decoding this            syntax element in CABAC encoder/decoder, same or different            context models may be used for AMVR and affine mode.        -   ii. Alternatively, furthermore, this syntax element may have            different semantics in AMVR and affine mode.    -   f. In one example, a new syntax element is used for coding the        MVD precision of affine mode, i.e., two different syntax        elements are used for coding the MVD precision of AMVR and        affine mode.    -   g. The syntax for indication of MVD precisions for the affine        mode may be signaled under one or all of the following        conditions are true:        -   i. MVDs for all control points are non-zero.        -   ii. MVDs for at least one control point is non-zero.        -   iii. MVD of one control point (e.g., the first CPMV) are            non-zero    -    In this case, when either one of the above conditions or all of        them fail, there is no need to signal the MVD precisions.    -   h. The syntax element for indication of MVD precisions for        either affine mode or the AMVR mode may be coded with contexts        and the contexts are dependent on coded information.        -   i. In one example, when there is only one single syntax            element, the contexts may depend on whether current block is            coded with affine mode or not.    -   i. In one example, the context may depend on the block        size/block shape/MVD precisions of neighboring blocks/temporal        layer index/prediction directions, etc. al.    -   j. Whether to enable or disable the usage of multiple MVD        precisions for the affine mode may be signaled in        SPS/PPS/VPS/sequence header/picture header/slice header/group of        CTUs, etc. al.        -   i. In one example, whether to signal the information of            enable or disable the usage of multiple MVD precisions for            the affine mode may depend on other syntax elements. For            example, the information of enable or disable the usage of            multiple MV and/or MVP and/or MVD precisions for the affine            mode is signaled when affine mode is enabled; and is not            signaled and inferred to be 0 when affine mode is disabled.    -   k. Alternatively, multiple syntax elements may be signaled to        indicate the used MV and/or MVP and/or MVD precision (in the        following discussion, they are all referred to as “MVD        precision”) in affine inter mode.        -   i. In one example, the syntax elements used to indicate the            used MVD precision in affine inter mode and normal inter            mode may be different.            -   1. The number of syntax elements to indicate the used                MVD precision in affine inter mode and normal inter mode                may be different.            -   2. The semantics of the syntax elements to indicate the                used MVD precision in affine inter mode and normal inter                mode may be different.            -   3. The context models in arithmetic coding to code one                syntax elements to indicate the used MVD precision in                affine inter mode and normal inter mode may be                different.            -   4. The methods to derive context models in arithmetic                coding to code one syntax element to indicate the used                MVD precision in affine inter mode and normal inter mode                may be different.        -   ii. In one example, a first syntax element (e.g. amvr_flag)            may be signaled to indicate whether to apply AMVR in an            affine-coded block.            -   1. The first syntax element is conditionally signaled.                -   a. In one example, signalling of the first syntax                    element (amvr_flag) is skipped when current block is                    coded with certain mode (e.g., CPR/IBC mode).                -   b. In one example, signalling of the first syntax                    element (amvr_flag) is skipped when all CPMVs' MVDs                    (including both horizontal and vertical components)                    are all zero.                -   c. In one example, signalling of the first syntax                    element (amvr_flag) is skipped when one selected                    CPMVs' MVDs (including both horizontal and vertical                    components) are all zero.                -    i. In one example, the selected CPMV's MVD is the                    first CPMV's MVD to be coded/decoded.                -   d. In one example, signalling of the first syntax                    element (amvr_flag) is skipped when the usage of                    enabling multiple MVD precisions for affine-coded                    block is false.                -   e. In one example, the first syntax element may be                    signaled under the following conditions:                -    i. Usage of enabling multiple MVD precisions for                    affine-coded block is true and current block is                    coded with affine mode;                -    ii. Alternatively, usage of enabling multiple MVD                    precisions for affine-coded block is true, current                    block is coded with affine mode, and at least one                    component of a CPMV's MVD is unequal to 0.                -    iii. Alternatively, usage of enabling multiple MVD                    precisions for affine-coded block is true, current                    block is coded with affine mode, and at least one                    component of a selected CPMV's MVD is unequal to 0.                -    1. In one example, the selected CPMV's MVD is the                    first CPMV's MVD to be coded/decoded.            -   2. When AMVR is not applied to an affine-coded block or                the first syntax element is not present, a default MV                and/or MVD precision is utilized.                -   f. In one example, the default precision is ¼-pel.                -   g. Alternatively, the default precision is set to                    that used in motion compensation for affine coded                    blocks.            -   3. For example, the MVD precision of affine mode is                ¼-pel if amvr_flag is equal to 0; otherwise the MVD                precision of affine mode may be other values.                -   h. Alternatively, furthermore, the additional MVD                    precisions may be further signaled via a second                    syntax element.        -   iii. In one example, a second syntax element (such as            amvr_coarse_precision_flag) may be signaled to indicate the            MVD precision of affine mode.            -   1. In one example, whether the second syntax element is                signaled may depend on the first syntax element. For                example, the second syntax element is only signaled when                the first syntax element is 1.            -   2. In one example, the MVD precision of affine mode is                1-pel if the second syntax element is 0; otherwise, the                MVD precision of affine mode is 1/16-pel.            -   3. In one example, the MVD precision of affine mode is                1/16-pel if the second syntax element is 0; otherwise,                the MVD precision of affine mode is full-pixel.        -   iv. In one example, a syntax element used to indicate the            used MVD precision in affine inter mode share the same            context models as the syntax element with the same name but            used to indicate the used MVD precision in normal inter            mode.            -   4. Alternatively, a syntax element used to indicate the                used MVD precision in affine inter mode use different                context models as the syntax element with the same name                but used to indicate the used MVD precision in normal                inter mode.

Example 10. Whether to apply or how to apply AMVR on an affine codedblock may depend on the reference picture of the current block.

-   -   a. In one example, AMVR is not applied if the reference picture        is the current picture, i.e., Intra block copying is applied in        the current block.

Fast Algorithm of AVMR in Affine Mode for Encoder

Denote RD cost (real RD cost, or SATD/SSE/SAD cost plus rough bits cost)of affine mode and AMVP mode as affineCosti and amvpCosti for IMV=i,where in i=0, 1 or 2. Here, IMV=0 means ¼ pel MV, and IMV=1 meansinteger MV for AMVP mode and 1/16 pel MV for affine mode, and IMV=2means 4 pel MV for AMVP mode and integer MV for affine mode. Denote RDcost of merge mode as mergeCost.

Example 11. It is proposed that AMVR is disabled for affine mode ofcurrent CU if the best mode of its parent CU is not AF_INTER mode orAF_MERGE mode.

Alternatively, AMVR is disabled for affine mode of current CU if thebest mode of its parent CU is not AF_INTER modeExample 12. It isproposed that AMVR is disabled for affine mode ifaffineCost0>th1*amvpCost0, wherein th1 is a positive threshold.

-   -   a. Alternatively, in addition, AMVR is disabled for affine mode        if min(affineCost0, amvpCost0)>th2*mergeCost, wherein th2 is a        positive threshold.    -   b. Alternatively, in addition, integer MV is disabled for affine        mode if affineCost0>th3*affineCost1, wherein th3 is a positive        threshold.

Example 12. It is proposed that AMVR is disabled for AMVP mode ifamvpCost0>th4*affineCost0, wherein th4 is a positive threshold.

-   -   a. Alternatively, AMVR is disabled for AMVP mode if        min(affineCost0, amvpCost0)>th5*mergeCost, wherein th5 is a        positive threshold.

Example 13. It is proposed that 4/6 parameter affine models obtained inone MV precision may be used as a candidate start search point for otherMV precisions.

-   -   b. In one example, 4/6 parameter affine models obtained in 1/16        MV may be used as a candidate start search point for other MV        precisions.    -   c. In one example, 4/6 parameter affine models obtained in ¼ MV        may be used as a candidate start search point for other MV        precisions.

Example 14. AMVR for affine mode is not checked at encoder for thecurrent block if its parent block does not choose the affine mode.

Example 15. Statistics of usage of different MV precisions foraffine-coded blocks in previously coded frames/slices/tiles/CTU rows maybe utilized to early terminate the rate-distortion calculations of MVprecisions for affine-coded blocks in current slice/tile/CTU row.

-   -   d. In one example, the percentage of affine-coded blocks with a        certain MV precision is recorded. If the percentage is too low,        then the checking of the corresponding MV precision is skipped.    -   e. In one example, previously coded frames with the same        temporal layer are utilized to decide whether to skip a certain        MV precision.

Context for Coding Affine AMVR

Example 16. For each context that is used for coding the affine AMVRcode, it is proposed to set a variable (denoted by shiftIdx) to controltwo probability updating speed associated with this context.

-   -   a. In one example, the faster updating speed is defined by        (shiftIdx>>2)+2.    -   b. In one example, the slower updating speed is defined by        (shiftIdx & 3)+3+shift0    -   c. In one example, the conformance bitstream shall follow the        rule that the derived faster updating speed shall be within [2,        5] inclusively.    -   d. In one example, the conformance bitstream shall follow the        rule that the derived faster updating speed shall be within [3,        6] inclusively.

Example 17. It is proposed that when coding the AMVR mode of one block,the neighboring block's affine AMVR mode information is disallowed forcontext modeling.

-   -   a. In one example, the neighboring block's AMVR mode index may        be utilized and neighboring block's affine AMVR mode information        is excluded. An example is shown in Table 1 (including Table 5-1        and 5-2), wherein (xNbL, yNbL) and (xNbA, yNbA) denotes the left        and above neighboring block. In one example, the context index        offset ctxInc=(condL && availableL)+(condA &&        availableA)+ctxSetIdx*3.

TABLE 1-1 Specification of ctxInc using left and above syntax elementsctxSet Syntax element condL condA Idx amvr_mode[ x0 ] amvr_mode[ xNbL ]amvr_mode[ xNbA ] 0 [ y0 ] [ yNbL ] [ yNbA ] ( inter_affine_flag &&!inter_affine_flag && !inter_affine_flag [ x0 ][ y0 ] is [ xNbL ][ yNbL] [ xNbL ][ yNbL ] equal to 0 )

TABLE 2-2 Specification of ctxInc using left and above syntax elementsctxSet Syntax element condL condA Idx amvr_flag[ x0 ] amvr_flag[ xNbL ]amvr_flag[ xNbA ] 0 [ y0 ] [ yNbL ] [ yNbA ] ( inter_affine_flag &&!inter_affine_flag && !inter_affine_flag [ x0 ][ y0 ] is [ xNbL ][ yNbL] [ xNbL ][ yNbL ] equal to 0 )

-   -   b. Alternatively, neighboring block's affine AMVR mode        information may be further utilized but with a function instead        of being directly used. In one example, the function func as        described in Table 3-1 may return true when the        amvr_mode[xNbL][yNbL] of an affine-coded neighboring block        indicates a certain MV precision (such as the ¼-pel MV        precision). In one example, the function func as described in        Table 3-2 may return true when the amvr_flag[xNbL][yNbL] of an        affine-coded neighboring block indicates a certain MV precision        (such as the ¼-pel MV precision).

TABLE 3-1 Specification of ctxInc using left and above syntax elementsctxSet Syntax element condL condA Idx amvr_mode[ x0 ][ y0 ] (amvr_mode[xNbL ][ yNbL ] amvr_mode[ xNbA ][ yNbA ] 0 ( inter_affine_flag &&!inter_affine_flag[ xNbL ] && !inter_affine_flag [ x0 ][ y0 ] is equalto [ yNbL ]) [ xNbL ][ yNbL ] 0 ) ∥( ∥( inter_affine_flag[ xNbL ]inter_affine_flag[ xNbL ] [ yNbL ] && [ yNbL ] && func(amvr_mode[ xNbL ]func(amvr_mode[ xNbL ] [ yNbL ])) [ yNbL ]))

TABLE 6-2 Specification of ctxInc using left and above syntax elementsctxSet Syntax element condL condA Idx amvr_flag[ x0 ] amvr_flag[ xNbL ]amvr_flag[ xNbA ] 0 [ y0 ] [ yNbL ] [ yNbA ] ( inter_affine_flag &&!inter_affine_flag && !inter_affine_flag [ x0 ][ y0 ] is [ xNbL ][ yNbL] [ xNbL ][ yNbL ] equal to 0 )

-   -   c. Alternatively, neighboring block's affine AMVR mode        information may be further utilized for coding the first syntax        element (e.g., amvr_flag) of the AMVR mode (which is applied to        normal inter mode). Table 6-3 and 6-4 give some examples.

TABLE 6-3 Specification of ctxInc using left and above syntax elementsctxSet Syntax element condL condA Idx amvr_flag[ x0 ] amvr_flag[ xNbL ]amvr_flag[ xNbA ] 0 [ y0 ] [ yNbL ] [ yNbA ] ( inter_affine_flag [ x0 ][y0 ] is equal to 0 )

TABLE 6-4 Specification of ctxInc using left and above syntax elementsctxSet Syntax element condL condA Idx amvr_flag[ x0 ] amvr_flag[ xNbL ]amvr_flag[ xNbA ] 0 [ y0 ] [ yNbL ] [ yNbA ] && !inter_affine_flag &&!inter_affine_flag [ x0 ][ y0 ] [ x0 ][ y0 ]

-   -   d. When the AMVR mode information is represented by multiple        syntax elements (e.g., the first and second syntax elements,        denoted by amvr_flag, amvr_coarse_precision_flag), the above        syntax amvr_mode may be replaced by any of the multiple syntax        elements and above methods may be still applied.

Example 18. It is proposed that when coding the Affine AMVR mode, theneighboring block's AMVR mode information may be utilized for contextcoding.

-   -   a. In one example, the neighboring block's AMVR mode information        is directly used. An example is shown in Table 4. Alternatively,        furthermore, the context index offset ctxInc=(condL &&        availableL)+(condA && availableA)+ctxSetIdx*3.

TABLE 4 Specification of ctxInc using left and above syntax elementsSyntax element condL condA ctxSetIdx amvr_mode amvr_mode amvr_mode 0 [x0 ][ y0 ] [ xNbL ] [ xNbA ] ( inter_affine_flag [ yNbL ] [ yNbA ] [ x0][ y0 ] is equal to 1 )

-   -   b. Alternatively, the neighboring block's AMVR mode information        is disallowed for context modeling. An example is shown in Table        5.

TABLE 5 Specification of ctxInc using left and above syntax elementsSyntax element condL condA ctxSetIdx amvr_mode amvr_mode amvr_mode 0 [x0 ][ y0 ] [ xNbL ][ yNbL ] [ xNbA ][ yNbA ] ( inter_affine_flag &&inter_affine_flag && inter_affine_flag [ x0 ][ y0 ] [ xNbL ][ yNbL ] [xNbL ][ yNbL ] is equal to 1 )

-   -   c. Alternatively, neighboring block's AMVR mode information may        be further utilized but with a function instead of being        directly used. In one example, the function func as described in        Table 6 may return true when the amvr_mode[xNbL][yNbL] of an        non-affine-coded neighboring block indicates a certain MV        precision (such as the ¼-pel MV precision).

TABLE 6 Specification of ctxInc using left and above syntax elementsSyntax element condL condA ctxSetIdx amvr_mode (amvr_mode amvr_mode 0 [x0 ][ y0 ] [ xNbL ][ yNbL ] [ xNbA ][ yNbA ] ( inter_affine_flag &&inter_affine_flag && inter_affine_flag [ x0 ][ y0 ] [ xNbL ][ yNbL ]) [xNbL ][ yNbL ] is equal to 1 ) ||( !inter_affine_flag ||(!inter_affine_flag [ xNbL ][ yNbL ] [ xNbL ][ yNbL ] && func(amvr_mode&& func(amvr_mode [ xNbL ][yNbL ])) [ xNbL ][yNbL ]))

-   -   d. When the affine AMVR mode information is represented by        multiple syntax elements (e.g., the first and second syntax        elements, denoted by amvr_flag, amvr_coarse_precision_flag), the        above syntax amvr_mode may be replaced by any of the multiple        syntax elements and above methods may be still applied.

Fast Algorithm of SMVD and Affine SMVD

When checking the SMVD mode, suppose the currently selected best mode isCurBestMode, and the AMVR MVD precision in AMVR is MvdPrec or the MVDprecision of affine AMVR is MvdPrecAff.

Example 19. SMVD mode may be skipped depending on the currently selectedbest mode (i.e., CurBestMode), the MVD precision in AMVR.

-   -   a. In one example, if the CurBestMode is merge mode or/and UMVE        mode, SMVD mode may be not checked.    -   b. In one example, if the CurBestMode is not coded with SMVD        mode, SMVD mode may be not checked.    -   c. In one example, if the CurBestMode is affine mode, SMVD mode        may be not checked.    -   d. In one example, if the CurBestMode is sub-block merge mode,        SMVD mode may be not checked.    -   e. In one example, if the CurBestMode is affine SMVD mode, SMVD        mode may be not checked.    -   f. In one example, if the CurBestMode is affine merge mode, SMVD        mode may be not checked.    -   g. In one example, above fast methods, i.e., bullet 0.a˜0.f, may        be applied only for some MVD precision.        -   i. In one example, above fast methods may be applied only            when MVD precision is greater than or equal to a precision            (for example, integer-pel precision).        -   ii. In one example, above fast methods may be applied only            when MVD precision is greater than a precision (for example,            integer-pel precision).        -   iii. In one example, above fast methods may be applied only            when MVD precision is smaller than or equal to a precision            (for example, integer-pel precision).        -   iv. In one example, above fast methods may be applied only            when MVD precision is smaller than a precision (for example,            integer-pel precision).

Example 20. Affine SMVD mode may be skipped depending on the currentlyselected best mode (i.e., CurBestMode), the MVD precision in affineAMVR.

-   -   a. In one example, if the CurBestMode is merge mode or/and UMVE        mode, affine SMVD mode may be not checked.    -   b. In one example, if the CurBestMode is not coded with affine        SMVD mode, affine SMVD mode may be not checked.    -   c. In one example, if the CurBestMode is sub-block merge mode,        affine SMVD mode may be not checked.    -   d. In one example, if the CurBestMode is SMVD mode, affine SMVD        mode may be not checked.    -   e. In one example, if the CurBestMode is affine merge mode,        affine SMVD mode may be not checked.    -   f. In one example, above fast methods, i.e., bullet 20.a to        20.e, may be applied only for some MVD precision.        -   i. In one example, above fast methods may be applied only            when affine MVD precision is greater than or equal to a            precision (for example, integer-pel precision).        -   ii. In one example, above fast methods may be applied only            when affine MVD precision is greater than a precision (for            example, integer-pel precision).        -   iii. In one example, above fast methods may be applied only            when affine MVD precision is smaller than or equal to a            precision (for example, integer-pel precision).        -   iv. In one example, above fast methods may be applied only            when affine MVD precision is smaller than a precision (for            example, integer-pel precision).

Example 21. The above proposed method may be applied under certainconditions, such as block sizes, slice/picture/tile types, or motioninformation.

-   -   a. In one example, when a block size contains smaller than M*H        samples, e.g., 16 or 32 or 64 luma samples, proposed method is        not allowed.    -   b. Alternatively, when minimum size of a block's width or/and        height is smaller than or no larger than X, proposed method is        not allowed. In one example, X is set to 8.    -   c. Alternatively, when minimum size of a block's width or/and        height is no smaller than X, proposed method is not allowed. In        one example, X is set to 8.    -   d. Alternatively, when a block's width >th1 or >=th1 and/or a        block's height >th2 or >=th2, proposed method is not allowed. In        one example, th1 and/or th2 is set to 8.    -   e. Alternatively, when a block's width <th1 or <=th1 and/or a        block's height <th2 or <a=th2, proposed method is not allowed.        In one example, th1 and/or th2 is set to 8.    -   f. Alternatively, whether to enable or disable the above methods        and/or which method to be applied may be dependent on block        dimension, video processing data unit (VPDU), picture type, low        delay check flag, coded information of current block (such as        reference pictures, uni or bi-prediction) or previously coded        blocks.

Example 22. The AMVR methods for affine mode may be performed indifferent ways when intra block copy (IBC, a.k.a. current picturereference (CPR)) is applied or not.

-   -   a. In one example, AMVR for affine mode cannot be used if a        block is coded by IBC.    -   b. In one example, AMVR for affine mode may be used if a block        is coded by IBC, but the candidate MV/MVD/MVP precisions may be        different to those used for non-IBC coded affine-coded block.

Example 23. All the term “slice” in the document may be replaced by“tile group” or “tile”.

Example 24. In VPS/SPS/PPS/slice header/tile group header, a syntaxelement (e.g. no_amvr_constraint_flag) equal to 1 specifies that it is arequirement of bitstream conformance that both the syntax element toindicate whether AMVR is enabled (e.g. sps_amvr_enabled_flag) and thesyntax element to indicate whether affine AMVR is enabled (e.g.sps_affine_avmr_enabled_flag) shall be equal to 0. The syntax element(e.g. no_amvr_constraint_flag) equal to 0 does not impose a constraint.

Example 25. In VPS/SPS/PPS/slice header/tile group header or other videodata units, a syntax element (e.g. no_affine_amvr_constraint_flag) maybe signalled.

-   -   a. In one example, no_affine_amvr_constraint_flag equal to 1        specifies that it is a requirement of bitstream conformance that        the syntax element to indicate whether affine AMVR is enabled        (e.g. sps_affine_avmr_enabled_flag) shall be equal to 0. The        syntax element (e.g. no_affine_amvr_constraint_flag) equal to 0        does not impose a constraint

Example 26. Multiple contexts may be utilized for coding the secondsyntax element which indicates the coarse motion precision (such asamvr_coarse_precision_flag).

-   -   a. In one example, two contexts may be utilized.    -   b. In one example, selection of contexts may depend on whether        the current block is affine coded or not.    -   c. In one example, for the first syntax, it may be coded with        only one context and also for the second syntax, it may be coded        with only one context.    -   d. In one example, for the first syntax, it may be coded with        only one context and also for the second syntax, it may be        bypass coded.    -   e. In one example, for the first syntax, it may be bypass coded        and also for the second syntax, it may be bypass coded.    -   f. In one example, for all syntax elements related to motion        vector precisions, they may be bypass coded.

Example 27. For example, only the first bin of the syntax elementamvr_mode is coded with arithmetic coding context(s). All the followingbins of amvr_mode are coded as bypass coding.

-   -   a. The above disclosed method may also be applied to other        syntax elements.    -   b. For example, only the first bin of the syntax element SE is        coded with arithmetic coding context(s). All the following bins        of SE are coded as bypass coding. SE may be

1) alf_ctb_flag 2) sao_merge_left_flag 3) sao_merge_up_flag 4)sao_type_idx_luma 5) sao_type_idx_chroma 6) split_cu_flag 7)split_qt_flag 8) mtt_split_cu_vertical_flag 9) mtt_split_cu_binary_flag10)cu_skip_flag 11)pred_mode_ibc_flag 12)pred_mode_flag13)intra_luma_ref_idx 14)intra_subpartitions_mode_flag15)intra_subpartition_split_flag 16)intra_luma_mpm_flag17)intra_chroma_pred_mode 18)merge_flag 19)inter_pred_idc20)inter_affine_flag 21)cu_affine_type_flag 22)ref_idx_10 23)mvp_10_flag24)ref_idx_11 25)mvp_11_flag 26)avmr_flag 27)amvr_precision_flag28)gbi_idx 29)cu_cbf 30)cu_sbt_flag 31)cu_sbt_quad_flag32)cu_sbt_horizontal_flag 33)cu_sbt_pos_flag 34)mmvd_flag35)mmvd_merge_flag 36)mmvd_distance_idx 37)ciip_flag38)ciip_luma_mpm_flag 39)merge_subblock_flag 40)merge_subblock_idx41)merge_triangle_flag 42)merge_triangle_idx0 43)merge_triangle_idx144)merge_idx 45)abs_mvd_greater0_flag 46)abs_mvd_greater1_flag47)tu_cbf_luma 48)tu_cbf_cb 49)tu_cbf_cr 50)cu_qp_delta_abs51)transform_skip_flag 52)tu_mts_idx 53)last_sig_coeff_x_prefix54)last_sig_coeff_y_prefix 55)coded_sub_block_flag 56)sig_coeff_flag57)par_level_flag 58)abs_level_gt1_flag 59)abs_level_gt3_flag

-   -   c. Alternatively, furthermore, if a syntax element SE is a        binary value (i.e., it could be only either equal to 0 or 1), it        may be context coded.        -   i. Alternatively, furthermore, if a syntax element SE is a            binary value (i.e., it could be only either equal to 0 or            1), it may be bypass coded.    -   d. Alternatively, furthermore, only 1 context may be used for        coding the first bin.

Example 28. The precision of motion vector prediction (MVP) or motionvector difference (MVD), or the reconstructed motion vector (MV) may bechanged depending on the motion precision which may be signaled.

-   -   a. In one example MVP=MVP<<s if the original prediction of MVP        is lower (or not higher) than the target precision. s is an        integer, which may depend on the difference between the original        precision and the target precision.        -   iii. Alternatively, MVD=MVD<<s if the original precision of            MVD is lower (or not higher) than the target precision. s is            an integer, which may depend on the difference between the            original precision and the target precision.        -   iv. Alternatively, MV=MV<<s if the original precision of MV            is lower (or not higher) than the target precision. s is an            integer, which may depend on the difference between the            original precision and the target precision.            -   b. In one example MVP=Shift(MVP, s) if the original                prediction of MVP is higher (or not lower) than the                target precision. s is an integer, which may depend on                the difference between the original precision and the                target precision.        -   v. Alternatively, MVD=Shift(MVD, s) if the original            precision of MVD is higher (or not lower) than the target            precision. s is an integer, which may depend on the            difference between the original precision and the target            precision.        -   vi. Alternatively, MV=Shift(MV, s) if the original precision            of MV is higher (or not lower) than the target precision. s            is an integer, which may depend on the difference between            the original precision and the target precision.            -   c. In one example MVP=SatShift(MVP, s) if the original                prediction of MVP is higher (or not lower) than the                target precision. s is an integer, which may depend on                the difference between the original precision and the                target precision.        -   vii. Alternatively, MVD=SatShift(MVD, s) if the original            precision of MVD is higher (or not lower) than the target            precision. s is an integer, which may depend on the            difference between the original precision and the target            precision.        -   viii. Alternatively, MV=SatShift(MV, s) if the original            precision of MV is higher (or not lower) than the target            precision. s is an integer, which may depend on the            difference between the original precision and the target            precision.            -   d. The above methods disclosed may be applied when the                current block is not coded with affine modes.            -   e. The above methods disclosed may be applied when the                current block is coded with affine modes.

1. EMBODIMENTS

Highlighted parts show the modified specification.

1.1. Embodiment 1: Indication of Usage of Affine AMVR Mode

It may be signaled in SPS/PPS/VPS/APS/sequence header/pictureheader/tile group header, etc. al. This section presents the signallingin SPS.

1.1.1. SPS Syntax Table

Descriptor seq_parameter_set_rbsp( ) {  sps_seq_parameter_set_id ue(v)...  sps_amvr_enabled_flag u(1)  sps_bdof_enabled_flag u(1) sps_affine_amvr_enabled_flag u(1)  sps_cclm_enabled_flag u(1) sps_mts_intra_enabled_flag u(1)  sps_mts_inter_enabled_flag u(1) sps_affine_enabled_flag u(1)  if( sps_affine_enabled_flag )  sps_affine_type_flag u(1)  sps_gbi_enabled_flag u(1) sps_cpr_enabled_flag u(1) ...  rbsp_trailing_bits( ) }

An alternative SPS syntax table is given as follows:

Descriptor seq_parameter_set_rbsp( ) {  sps_seq_parameter_set_id ue(v) sps_amvr_enabled_flag u(1)  sps_bdof_enabled_flag u(1) sps_cclm_enabled_flag u(1)  sps_mts_intra_enabled_flag u(1) sps_mts_inter_enabled_flag u(1)  sps_affine_enabled_flag u(1)  if(sps_affine_enabled_flag ){    sps_affine_type_flag u(1)  sps_affine_amvr_enabled_flag u(1) }  sps_gbi_enabled_flag u(1) sps_cpr_enabled_flag u(1)  sps_ciip_enabled_flag u(1) sps_triangle_enabled_flag u(1)  sps_ladf_enabled_flag u(1) ... rbsp_trailing_bits( ) }

Semantics:

-   -   sps_affine_amvr_enabled_flag equal to 1 specifies that adaptive        motion vector difference resolution is used in motion vector        coding of affine inter mode. amvr_enabled_flag equal to 0        specifies that adaptive motion vector difference resolution is        not used in motion vector coding of affine inter mode.

1.2. Parsing Process of Affine AMVR Mode Information

Syntax of the affine AMVR mode information may reuse that for the AMVRmode information (applied to normal inter mode). Alternatively,different syntax elements may be utilized.

Affine AMVR mode information may be conditionally signaled. Differentembodiments below show some examples of the conditions.

1.2.1. Embodiment #1: CU Syntax Table

Descriptor coding_unit( x0, y0, cbWidth, cbHeight, treeType ) {  if(tile group type != I ) {   if( treeType != DUAL_TREE_CHROMA )   cu_skip_flag[ x0 ][ y0 ] ae(v)   if( cu_skip_flag [ x0 ][ y0 ] = = 0)    pred_mode_flag ae(v)  }  if( CuPredMode [ x0 ][ y0 ] = = MODE_INTRA) { ...   }  } else if( treeType != DUAL_TREE_CHROMA ) { /* MODE_INTER*/   if( cu_skip_flag[ x0 ][ y0 ] = = 0 )    merge_flag[ x0 ][ y0 ]ae(v)   if( merge_flag[ x0 ][ y0 ] ) {    merge_data( x0, y0, cbWidth,cbHeight )   } else {    if( tile_group_type = = B )     inter_pred_idc[x0 ][ y0 ] ae(v)    if( sps_affine_enabled_flag && cbWidth >= 16 &&cbHeight >= 16 ) {     inter_affine_flag[ x0 ] [y0 ] ae(v)     if(sps_affine_type_flag && inter_affine_flag[ x0 ][ y0 ] )     cu_affine_type_flag[ x0 ][ y0 ] ae(v)     }     if( inter_pred_idc[x0 ][ y0 ] != PRED_L1 ) {      if( num_ref_idx_l0_active_minus1 > 0 )      ref_idx_l0[ x0 ][ y0 ] ae(v)      mvd_coding( x0, y0, 0, 0 )     if( MotionModelIdc[ x0 ][ y0 ] > 0 )       mvd_coding( x0, y0, 0, 1)      if(MotionModelIdc[ x0 ][ y0 ] > 1 )       mvd_coding( x0, y0, 0,2 )      mvp_l0_flag[ x0 ][ y0 ] ae(v)     } else {      MvdL0[ x0 ][ y0][ 0 ] = 0      MvdL0[ x0 ][ y0 ][ 1 ] = 0     }     if( inter_pred_idc[x0 ][ y0 ] != PRED_L0 ) }      if( num_ref_idx_l1_active_minus1 > 0 )      ref_idx_l1[ x0 ][ y0 ] ae(v)      if( mvd_l1_zero_flag &&inter_pred_idc[ x0 ][ y0 ] = = PRED_BI ) {       MvdL1[ x0 ][ y0 ][ 0 ]= 0       MvdL1[ x0 ][ y0 ][ 1 ] = 0       MvdCpL1[ x0 ][ y0 ][ 0 ][ 0 ]= 0       MvdCpL1[ x0 ][ y0 ][ 0 ][ 1 ] = 0       MvdCpL1[ x0 ][ y0 ][ 1][ 0 ] = 0       MvdCpL1[ x0 ][ y0 ][ 1 ][ 1 ] = 0       MvdCpL1[ x0 ][y0 ][ 2 ][ 0 ] = 0       MvdCpL1[ x0 ][ y0 ][ 2 ][ 1 ] = 0      } else {      mvd_coding( x0, y0, 1, 0 )      if( MotionModelIdc[ x0 ][ y0 ] > 0)       mvd_coding( x0, y0, 1, 1 )      if(MotionModelIdc[ x0 ][ y0 ] >1 )       mvd_coding( x0, y0, 1, 2 )      mvp_l1_flag[ x0 ][ y0 ] ae(v)    } else {      MvdL1[ x0 ][ y0 ][ 0 ] = 0      MvdL1[ x0 ][ y0 ][ 1 ]= 0     }     if( ( sps_amvr_enabled_flag && inter_affine_flag = = 0 &&     ( MvdL0[ x0 ][ y0 ][ 0 ] != 0 | | MvdL0[ x0 ][ y0 ][ 1 ] != 0 | |     MvdL1[ x0 ][ y0 ][ 0 ] != 0 | | MvdL1[ x0 ][ y0 ][ 1 ] != 0 ) ) ∥     ( sps_affine_amvr_enabled_flag && inter_affine_flag = = 1 &&      (MvdCpL0[ x0 ][ y0 ][ 0 ][ 0 ] != 0 | | MvdCpL0[ x0 ][ y0 ][ 0 ][ 1 ] !=0 | |      MvdCpL1[ x0 ][ y0 ][ 0 ][ 0 ] != 0 | | MvdCpL1[ x0 ][ y0 ][ 0][ 1 ] != 0 | |      MvdCpL0[ x0 ][ y0 ][ 1 ][ 0 ] != 0 | | MvdCpL0[ x0][ y0 ][ 1 ][ 1 ] != 0 | |      MvdCpL1[ x0 ][ y0 ][ 1 ][ 0 ] != 0 | |MvdCpL1[ x0 ][ y0 ][ 1 ][ 1 ] != 0 | |      MvdCpL0[ x0 ][ y0 ][ 2 ][ 0] != 0 | | MvdCpL0[ x0 ][ y0 ][ 2 ][ 1 ] != 0 | |      MvdCpL1[ x0 ][ y0][ 2 ][ 0 ] != 0 | | MvdCpL1[ x0 ][ y0 ][ 2 ][ 1 ] ! = 0 ) ) ) {     if( !sps cpr enabled flag | | !( inter_pred_idc[ x0 ][ y0 ] = =PRED_L0 &&  ref_idx_l0[ x0 ][ y0 ] = = num_ref_idx_l0_active_minus1 ) )      amvr_flag[ x0 ][ y0 ] ae(v)      if( amvr_flag[ x0 ][ y0 ] )      amvr_coarse_precisoin_flag[ x0 ][ y0 ] ae(v)     }     if(sps_gbi_enabled_flag && inter_pred_idc[ x0 ][ y0 ] = = PRED_BI &&     cbWidth * cbHeight >= 256 )      gbi_idx[ x0 ][ y0 ] ae(v)    }  } if( !pcm_flag[ x0 ][ y0 ] ) {    if( CuPredMode[ x0 ][ y0 ] !=MODE_INTRA && cu_skip_flag[ x0 ][ y0 ] = = 0 )     cu_cbf ae(v)    if(cu_cbf )     transform_tree( x0, y0, cbWidth, cbHeight, treeType )  } }

1.2.2. Embodiment 2: An Alternative CU Syntax Table Design

Descriptor coding_unit( x0, y0, cbWidth, cbHeight, treeType ) {  if(tile_group_type != I ) {   if( treeType != DUAL_TREE_CHROMA )   cu_skip_flag[ x0 ][ y0 ] ae(v)   if( cu_skip_flag[ x0 ][ y0 ] = = 0 )   pred_mode_flag ae(v)  }  if( CuPredMode[ x0 ][ y0 ] = = MODE_INTRA ){ ...   }  } else if( treeType != DUAL_TREE_CHROMA ) { /* MODE_INTER */  if( cu_skip_flag[ x0 ][ y0 ] = = 0 )    merge_flag[ x0 ][ y0 ] ae(v)  if( merge_flag[ x0 ][ y0 ] ) {    merge_data( x0, y0, cbWidth,cbHeight )   } else {    if( tile_group_type = = B )     inter_pred_idc[x0 ][ y0 ] ae(v)    if( sps_affine_enabled_flag && cbWidth >= 16 &&cbHeight >= 16 ) {     inter_affine_flag[ x0 ][ y0 ] ae(v)     if(sps_affine_type_flag && inter_affine_flag[ x0 ][ y0 ] )     cu_affine_type_flag[ x0 ][ y0 ] ae(v)    }    if( inter_pred_idc[x0 ][ y0 ] != PRED_L1 ) {     if( num_ref_idx_l0_active_minus1 > 0 )     ref_idx_l0[ x0 ][ y0 ] ae(v)     mvd_coding( x0, y0, 0, 0 )     if(MotionModelIdc[ x0 ][ y0 ] > 0 )      mvd_coding( x0, y0, 0, 1 )    if(MotionModelIdc[ x0 ][ y0 ] > 1 )      mvd_coding( x0, y0, 0, 2 )    mvp_l0_flag[ x0 ][ y0 ] ae(v)    } else {     MvdL0[ x0 ][ y0 ][ 0 ]= 0     MvdL0[ x0 ][ y0 ][ 1 ] = 0    }    if( inter_pred_idc[ x0 ][ y0] != PRED_L0 ) {     if( num_ref_idx_l1_active_minus1 > 0 )     ref_idx_l1[ x0 ][ y0 ] ae(v)     if( mvd_l1_zero_flag &&inter_pred_idc[ x0 ][ y0 ] = = PRED_BI ) {       MvdL1[ x0 ][ y0 ][ 0 ]= 0       MvdL1[ x0 ][ y0 ][ 1 ] = 0       MvdCpL1[ x0 ][ y0 ][ 0 ][ 0 ]= 0       MvdCpL1[ x0 ][ y0 ][ 0 ][ 1 ] = 0       MvdCpL1[ x0 ][ y0 ][ 1][ 0 ] = 0       MvdCpL1[ x0 ][ y0 ][ 1 ][ 1 ] = 0       MvdCpL1[ x0 ][y0 ][ 2 ][ 0 ] = 0       MvdCpL1[ x0 ][ y0 ][ 2 ][ 1 ] = 0     } else {      mvd_coding( x0, y0, 1, 0 )     if( MotionModelIdc[ x0 ][ y0 ] > 0)       mvd_coding( x0, y0, 1, 1 )     if(MotionModelIdc[ x0 ][ y0 ] > 1)       mvd_coding( x0, y0, 1, 2 )     mvp_l1_flag[ x0 ][ y0 ] ae(v)   } else {     MvdL1[ x0 ][ y0 ][ 0 ] = 0     MvdL1[ x0 ][ y0 ][ 1 ] =0    }    if( ( sps_amvr_enabled_flag && inter_affine_flag = = 0 &&    ( MvdL0[ x0 ][ y0 ][ 0 ] != 0 | | MvdL0[ x0 ][ y0 ][ 1 ] != 0 | |    MvdL1[ x0 ][ y0 ][ 0 ] != 0 | | MvdL1[ x0 ][ y0 ][ 1 ] != 0 ) ) ∥    ( sps_affine_amvr_enabled_flag && inter_affine_flag = = 1 &&     (MvdCpL0[ x0 ][ y0 ][ 0 ][ 0 ] != 0 | | MvdCpL0[ x0 ][ y0 ][ 0 ][ 1 ] !=0 | |     MvdCpL1[ x0 ][ y0 ][ 0 ][ 0 ] != 0 | | MvdCpL1[ x0 ][ y0 ][ 0][ 1 ] != 0 ) ) ) {     if( !sps_cpr_enabled_flag | | !( inter_pred_idc[x0 ][ y0 ] = = PRED_L0 &&  ref_idx_l0[ x0 ][ y0 ] = =num_ref_idx_l0_active_minus1 ) )      amvr_flag[ x0 ][ y0 ] ae(v)    if( amvr_flag[ x0 ][ y0 ] )      amvr_coarse_precisoin_flag[ x0 ][y0 ] ae(v)    }    if( sps_gbi_enabled_flag && inter_pred_idc[ x0 ][ y0] = = PRED_BI &&     cbWidth * cbHeight >= 256 )     gbi_idx[ x0 ][ y0 ]ae(v)   }  }  if( !pcm_flag[ x0 ][ y0 ] ) {   if( CuPredMode[ x0 ][ y0 ]!= MODE_INTRA && cu_skip_flag[ x0 ][ y0 ] = = 0 )     cu_cbf ae(v)   if( cu_cbf )     transform_tree( x0, y0, cbWidth, cbHeight, treeType)  } }

1.2.3. Embodiment 3: A ThirdCU Syntax Table Design

Descriptor coding_unit( x0, y0, cbWidth, cbHeight, treeType ) {  if(tile_group_type != I ) {   if( treeType != DUAL_TREE_CHROMA )   cu_skip_flag[ x0 ][ y0 ] ae(v)   if( cu_skip_flag[ x0 ][ y0 ] = = 0 )   pred_mode_flag ae(v)  }  if( CuPredMode[ x0 ][ y0 ] = = MODE_INTRA ){ ...   }  } else if( treeType != DUAL_TREE_CHROMA ) { /* MODE_INTER */  if( cu_skip_flag[ x0 ][ y0 ] = = 0 )    merge_flag[ x0 ][ y0 ] ae(v)  if( merge_flag[ x0 ][ y0 ] ) {    merge_data( x0, y0, cbWidth,cbHeight )   } else {    if( tile_group_type = = B )     inter_pred_idc[x0 ][ y0 ] ae(v)    if( sps_affine_enabled_flag && cbWidth >= 16 &&cbHeight >= 16 ) {     inter_affine_flag[ x0 ][ y0 ] ae(v)     if(sps_affine_type_flag && inter_affine_flag[ x0 ][ y0 ] )      cu_affine_type_flag[ x0 ][ y0 ] ae(v)     }     if(inter_pred_idc[ x0 ][ y0 ] != PRED_L1 ) {      if(num_ref_idx_l0_active_minus1 > 0 )       ref_idx_l0[ x0 ][ y0 ] ae(v)     mvd_coding( x0, y0, 0, 0 )      if( MotionModelIdc[ x0 ][ y0 ] > 0)       mvd_coding( x0, y0, 0, 1 )      if(MotionModelIdc[ x0 ][ y0 ] >1 )       mvd_coding( x0, y0, 0, 2 )      mvp_l0_flag[ x0 ][ y0 ] ae(v)    } else {      MvdL0[ x0 ][ y0 ][ 0 ] = 0      MvdL0[ x0 ][ y0 ][ 1 ]= 0     }     if( inter_pred_idc[ x0 ][ y0 ] != PRED_L0 ) {      if(num_ref_idx_l1_active_minus1 > 0 )       ref_idx_l1[ x0 ][ y0 ] ae(v)     if( mvd_l1_zero_flag && inter_pred_idc[ x0 ][ y0 ] = = PRED_BI ) {      MvdL1[ x0 ][ y0 ][ 0 ] = 0       MvdL1[ x0 ][ y0 ][ 1 ] = 0      MvdCpL1[ x0 ][ y0 ][ 0 ][ 0 ] = 0       MvdCpL1[ x0 ][ y0 ][ 0 ][1 ] = 0       MvdCpL1[ x0 ][ y0 ][ 1 ][ 0 ] = 0       MvdCpL1[ x0 ][ y0][ 1 ][ 1 ] = 0       MvdCpL1[ x0 ][ y0 ][ 2 ][ 0 ] = 0       MvdCpL1[x0 ][ y0 ][ 2 ][ 1 ] = 0      } else {       mvd_coding( x0, y0, 1, 0 )     if( MotionModelIdc[ x0 ][ y0 ] > 0 )       mvd_coding( x0, y0, 1, 1)      if(MotionModelIdc[ x0 ][ y0 ] > 1 )       mvd_coding( x0, y0, 1,2 )      mvp_l1_flag[ x0 ][ y0 ] ae(v)     } else {       MvdL1[ x0 ][y0 ][ 0 ] = 0       MvdL1[ x0 ][ y0 ][ 1 ] = 0     }     if( (sps_amvr_enabled_flag && inter_affine_flag = = 0 &&       ( MvdL0[ x0 ][y0 ][ 0 ] != 0 | | MvdL0[ x0 ][ y0 ][ 1 ] != 0 | |       MvdL1[ x0 ][ y0][ 0 ] != 0 | | MvdL1[ x0 ][ y0 ][ 1 ] != 0 ) ) ∥       (sps_affine_amvr_enabled_flag && inter_affine_flag = = 1) ) {       if(!sps_cpr_enabled_flag | | !( inter_pred_idc[ x0 ][ y0 ] = = PRED_L0 && ref_idx_l0[ x0 ][ y0 ] = = num_ref_idx_l0_active_minus1 ) )       amvr_flag[ x0 ][ y0 ] ae(v)       if( amvr_flag[ x0 ][ y0 ] )       amvr_coarse_precisoin_flag[ x0 ][ y0 ] ae(v)     }     if(sps_gbi_enabled_flag && inter_pred_idc[ x0 ][ y0 ] = = PRED_BI &&      cbWidth * cbHeight >= 256 )       gbi_idx[ x0 ][ y0 ] ae(v)   }  } if( !pcm_flag[ x0 ][ y0 ] ) {   if( CuPredMode[ x0 ][ y0 ] !=MODE_INTRA && cu_skip_flag[ x0 ][ y0 ] = = 0 )     cu_cbf ae(v)   if(cu_cbf )     transform_tree( x0, y0, cbWidth, cbHeight, treeType )  } }

1.2.4. Embodiment 4: Syntax Table Design with Different Syntax for AMVRand Affine AMVR Mode

coding_unit( x0, y0, cbWidth, cbHeight, treeType) {  if(tile_group_type_!= I ) {   if( treeType != DUAL_TREE_CHROMA )   cu_skip_flag[ x0 ][ y0 ]   if( cu_skip_flag[ x0 ][ y0 ] = = 0 )   pred_mode_flag  }  if( CuPredMode[ x0 ][ y0 ] = = MODE_INTRA ) { ...  }  } else if( treeType != DUAL_TREE_CHROMA )  { /* MODE_INTER */   if(cu_skip_flag[ x0 ][ y0 ] = = 0 )    merge_flag[ x0 ][ y0 ]   if(merge_flag[ x0 ][ y0 ] ) {    merge_data( x0, y0, cbWidth, cbHeight )  } else {    if( tile_group_type = = B )     inter_pred_idc[ x0 ][ y0 ]   if( sps_affine_enabled_flag && cbWidth >= 16 && cbHeight >= 16 ) {    inter_affine_flag[ x0 ][ y0 ]     if( sps_affine_type_flag &&inter_affine_flag[ x0 ][ y0 ] )      cu_affine_type_flag[ x0 ][ y0 ]   }    if( inter_pred_idc[ x0 ][ y0 ] != PRED_L1 ) {     if(num_ref_idx_10_active_minus1 > 0 )      ref_idx_10[ x0 ][ y0 ]    mvd_coding( x0, y0, 0, 0 )     if( MotionModelIdc[ x0 ][ y0 ] > 0 )     mvd_coding( x0, y0, 0, 1 )     if(MotionModelIdc[ x0 ][ y0 ] > 1 )     mvd_coding( x0, y0, 0, 2 )     mvp_10_flag[ x0 ][ y0 ]    } else {    MvdL0[ x0 ][ y0 ][ 0 ] = 0     MvdL0[ x0 ][ y0 ][ 1 ] = 0    }   if( inter_pred_idc[ x0 ][ y0 ] != PRED_L0 ) {     if(num_ref_idx_11_active_minus1 > 0 )      ref_idx_11[ x0 ][ y0 ]     if(mvd_11_zero_flag && inter_pred_idc [ x0 ][ y0 ] = = PRED_BI ) {     MvdL1[ x0 ][ y0 ][ 0 ] = 0      MvdL1[ x0 ][ y0 ][ 1 ] = 0     MvdCpL1[ x0 ][ y0 ][ 0 ][ 0 ] = 0      MvdCpL1[ x0 ][ y0 ][ 0 ][ 1] = 0      MvdCpL1[ x0 ][ y0 ][ 1 ][ 0 ] = 0      MvdCpL1[ x0 ][ y0 ][ 1][ 1 ] = 0      MvdCpL1[ x0 ][ y0 ][ 2 ][ 0 ] = 0      MvdCpL1[ x0 ][ y0][ 2 ][ 1 ] = 0     } else {      mvd_coding( x0, y0, 1, 0 )     if(MotionModelIdc[ x0 ][ y0 ] > 0 )      mvd_coding( x0, y0, 1, 1 )    if(MotionModelIdc[ x0 ][ y0 ] > 1 )      mvd_coding( x0, y0, 1, 2 )    mvp_11_flag[ x0 ][ y0 ]    } else {     MvdL1[ x0 ][ y0 ][ 0 ] = 0    MvdL1[ x0 ][ y0 ][ 1 ] = 0    }    if(sps_amvr_enabled_flag &&inter_affine_flag = =     0 && ( MvdL0[ x0 ][ y0 ][ 0 ] != 0 ∥ MvdL0[ x0][ y0 ][ 1 ] != 0 ∥     MvdL1[ x0 ][ y0 ][ 0 ] != 0 ∥ MvdL1[ x0 ][ y0 ][1] != 0 )) {     if( !sps_cpr_enabled_flag ∥ !( inter_pred_idc[ x0 ][ y0] = = PRED_L0 &&  ref_idx_10[ x0 ][ y0 ] = = num_ref_idx_10_active_minus1 ) )      amvr_flag[ x0 ][ y0 ]     if(amvr_flag[ x0 ][ y0 ] )      amvr_coarse_precisoin_flag[ x0 ][ y0 ]    }else if (conditionsA) {     if(conditionsB)      affine_amvr_flag[ x0 ][y0 ]     if( amvr_flag[ x0 ][ y0 ] )     affine_amvr_coarse_precisoin_flag[ x0 ][ y0 ]    }    if(sps_gbi_enabled_flag && inter_pred_idc [ x0 ][ y0 ] = = PRED_BI &&    cbWidth * cbHeight >= 256 )     gbi_idx[ x0 ][ y0 ]   }  }  if(!pcm_flag[ x0 ][ y0 ] ) {   if( CuPredMode[ x0 ][ y0 ] != MODE_INTRA &&cu_skip_flag[ x0 ][ y0 ] = = 0 )    cu_cbf   if( cu_cbf )   transform_tree( x0, y0, cbWidth, cbHeight, treeType )  } }

-   -   In one example, conditionsA is defined as follows:

  ( sps_affine_amvr_enabled_flag && inter_affine_flag = = 1 &&  (MvdCpL0[ x0 ][ y0 ][ 0 ][ 0 ] != 0 ∥ MvdCpL0[ x0 ][ y0 ][ 0 ][ 1 ] != 0∥  MvdCpL1[ x0 ][ y0 ][ 0 ][ 0 ] != 0 ∥ MvdCpL1[ x0 ][ y0 ][ 0 ][ 1 ] !=0 ∥  MvdCpL0[ x0 ][ y0 ][ 1 ][ 0 ] != 0 ∥ MvdCpL0[ x0 ][ y0 ][ 1 ][ 1 ]!= 0 ∥  MvdCpL1[ x0 ][ y0 ][ 1 ][ 0 ] != 0 ∥ MvdCpL1[ x0 ][ y0 ][ 1 ][ 1] != 0 ∥  MvdCpL0[ x0 ][ y0 ][ 2 ][ 0 ] != 0 ∥ MvdCpL0[ x0 ][ y0 ][ 2 ][1 ] != 0 ∥  MvdCpL1[ x0 ][ y0 ][ 2 ][ 0 ] != 0 ∥ MvdCpL1[ x0 ][ y0 ][ 2][ 1 ] != 0 ∥

Alternatively, conditionsA is defined as follows:

  ( sps_affine_amvr_enabled_flag && inter_affine_flag = = 1 &&  (MvdCpL0[ x0 ][ y0 ][ 0 ][ 0 ] != 0 ∥ MvdCpL0[ x0 ][ y0 ][ 0 ][ 1 ] != 0∥  MvdCpL1[ x0 ][ y0 ][ 0 ][ 0 ] != 0 ∥ MvdCpL1[ x0 ][ y0 ][ 0 ][ 1 ] !=0 ∥

Alternatively, conditionsA is defined as follows:

  ( sps_affine_amvr_enabled_flag && inter_affine_flag = = 1 &&  (MvdCpLX[ x0 ][ y0 ][ 0 ][ 0 ] != 0 ∥ MvdCpLX[ x0 ][ y0 ][ 0 ][ 1 ] != 0)wherein X is being 0 or 1.

Alternatively, conditionsA is defined as follows:

-   -   (sps_affine_amvr_enabled_flag && inter_affine_flag==1)    -   In one example, conditionsB is defined as follows:

  !sps_cpr_enabled_flag ∥ !( inter_pred_idc[ x0 ][ y0 ] = = PRED_L0 && ref_idx_10[ x0 ][ y0 ] = = num_ref_idx_10_active_minus1 )

Alternatively, conditionsB is defined as follows:

-   -   !sps_cpr_enabled_flag∥!(pred_mode[x0][y0]==CPR).

Alternatively, conditionsB is defined as follows:

-   -   !sps_ibc_enabled_flag∥!(pred_mode[x0][y0]==IBC).

When different syntax elements are utilized to code AMVR or Affine AMVR,the context modeling and/or contexts used for the embodiments in 5.5which are applied to Affine AMVR may be applied accordingly.

1.2.5. Semantics

amvr_flag[x0][y0] specifies the resolution of motion vector difference.The array indices x0, y0 specify the location (x0, y0) of the top-leftluma sample of the considered coding block relative to the top-left lumasample of the picture. amvr_flag[x0][y0] equal to 0 specifies that theresolution of the motion vector difference is ¼ of a luma sample.amvr_flag[x0][y0] equal to 1 specifies that the resolution of the motionvector difference is further specified byamvr_coarse_precision_flag[x0][y0].

When amvr_flag[x0][y0] is not present, it is inferred as follows:

-   -   If sps_cpr_enabled_flag is equal to 1, amvr_flag[x0][y0] is        inferred to be equal to 1.    -   Otherwise (sps_cpr_enabled_flag is equal to 0),        amvr_flag[x0][y0] is inferred to be equal to 0.

amvr_coarse_precision_flag[x0][y0] equal to 1 specifies that theresolution of the motion vector difference is four luma samples wheninter_affine_flag is equal to 0, and 1 luma samples wheninter_affine_flag is equal to 1. The array indices x0, y0 specify thelocation (x0, y0) of the top-left luma sample of the considered codingblock relative to the top-left luma sample of the picture.

When amvr_coarse_precision_flag[x0][y0] is not present, it is inferredto be equal to 0. If inter_affine_flag[x0][y0] is equal to 0, thevariable MvShift is set equal to(amvr_flag[x0][y0]+amvr_coarse_precision_flag[x0][y0])<<1 and thevariables MvdL0[x0][y0][0], MvdL0[x0][y0][1], MvdL1[x0][y0][0],MvdL1[x0][y0][1] are modified as follows:

MvdL0[x0][y0][0]=MvdL0[x0][y0][0]<<(MvShift+2)  (7-70)

MvdL0[x0][y0][1]=MvdL0[x0][y0][1]<<(MvShift+2)  (7-71)

MvdL1[x0][y0][0]=MvdL1[x0][y0][0]<<(MvShift+2)  (7-72)

MvdL1[x0][y0][1]=MvdL1[x0][y0][1](MvShift+2)  (7-73)

If inter_affine_flag[x0][y0] is equal to 1, the variable MvShift is setequal to (amvr_coarse_precision_flag ?(amvr_coarse_precision_flag<<1):(−(amvr_flag<<1))) and the variablesMvdCpL0[x0][y0][0][0], MvdCpL0[x0][y0][0][1], MvdCpL0[x0][y0][1][0],MvdCpL0[x0][y0][1][1], MvdCpL0[x0][y0][2][0], MvdCpL0[x0][y0][2][1] aremodified as follows:

MvdCpL0[x0][y0][0][0]=MvdCpL0[x0][y0][0][0]<<(MvShift+2)  (7-73)

MvdCpL1[x0][y0][0][1]=MvdCpL1[x0][y0][0][1]<<(MvShift+2)  (7-67)

MvdCpL0[x0][y0][1][0]=MvdCpL0[x0][y0][1][0]<<(MvShift+2)  (7-66)

MvdCpL1[x0][y0][1][1]=MvdCpL1[x0][y0][1][1]<<(MvShift+2)  (7-67)

MvdCpL0[x0][y0][2][0]=MvdCpL0[x0][y0][2][0]<<(MvShift+2)  (7-66)

MvdCpL1[x0][y0][2][1]=MvdCpL1[x0][y0][2][1]<<(MvShift+2)(7-67)

Alternatively, if inter_affine_flag[x0][y0] is equal to 1, the variableMvShift is set equal to (affine_amvr_coarse_precision_flag ?(affine_amvr_coarse_precision_flag<<1):(−(affine amvr_flag<<1))).

1.3. Rounding Process for Motion Vectors

The rounding process is modified that when the given rightShift value isequal to 0 (which happens for 1/16-pel precision), the rounding offsetis set to 0 instead of (1<<(rightShift−1)).

For example, the sub-clause of rounding process for MVs is modified asfollows:

Inputs to this process are:

-   -   the motion vector mvX,    -   the right shift parameter rightShift for rounding,    -   the left shift parameter leftShift for resolution increase.

Output of this process is the rounded motion vector mvX.

For the rounding of mvX, the following applies:

   offset = ( rightShift == 0 ) ? 0 : (1 << ( rightShift − 1)) (8-371)  mvX[ 0 ] = ( mvX[ 0 ] >= 0 ? ( mvX[ 0 ] + offset ) >>     rightShift :− ( ( −mvX[ 0 ] + offset ) >>     rightShift ) ) << leftShift (8-372)mvX[ 1 ] = ( mvX[ 1 ] >= 0 ? ( mvX[ 1 ] + offset ) >>    rightShift : −( ( −mvX[ 1 ] + offset ) >> (8-373)    rightShift ) ) << leftShift

1.4. Decoding Process

The rounding process invoked in the affine motion vector derivationprocess are performed with the input of (MvShift+2) instead of beingfixed to be 2.

Derivation process for luma affine control point motion vectorpredictors Inputs to this process are:

-   -   a luma location (xCb, yCb) of the top-left sample of the current        luma coding block relative to the top-left luma sample of the        current picture,    -   two variables cbWidth and cbHeight specifying the width and the        height of the current luma coding block,    -   the reference index of the current coding unit refIdxLX, with X        being 0 or 1,    -   the number of control point motion vectors numCpMv.

Output of this process are the luma affine control point motion vectorpredictors mvpCpLX[cpIdx] with X being 0 or 1, and cpIdx=0 . . .numCpMv−1.

For the derivation of the control point motion vectors predictorcandidate list, cpMvpListLX with X being 0 or 1, the following orderedsteps apply:

The number of control point motion vector predictor candidates in thelist numCpMvpCandLX is set equal to 0.

The variables availableFlagA and availableFlagB are both set equal toFALSE.

. . .

The rounding process for motion vectors as specified in clause 8.4.2.14is invoked with mvX set equal to cpMvpLX[cpIdx], rightShift set equal to(MvShift+2), and leftShift set equal to (MvShift+2) as inputs and therounded cpMvpLX[cpIdx] with cpIdx=0 . . . numCpMv−1 as output.

. . .

The variable availableFlagA is set equal to TRUE

The derivation process for luma affine control point motion vectors froma neighbouring block as specified in clause 8.4.4.5 is invoked with theluma coding block location (xCb, yCb), the luma coding block width andheight (cbWidth, cbHeight), the neighbouring luma coding block location(xNb, yNb), the neighbouring luma coding block width and height (nbW,nbH), and the number of control point motion vectors numCpMv as input,the control point motion vector predictor candidates cpMvpLY[cpIdx] withcpIdx=0 . . . numCpMv−1 as output.

The rounding process for motion vectors as specified in clause 8.4.2.14is invoked with mvX set equal to cpMvpLY[cpIdx], rightShift set equal to(MvShift+2), and leftShift set equal to (MvShift+2) as inputs and therounded cpMvpLY[cpIdx] with cpIdx=0 . . . numCpMv−1 as output.

The derivation process for luma affine control point motion vectors froma neighbouring block as specified in clause 8.4.4.5 is invoked with theluma coding block location (xCb, yCb), the luma coding block width andheight (cbWidth, cbHeight), the neighbouring luma coding block location(xNb, yNb), the neighbouring luma coding block width and height (nbW,nbH), and the number of control point motion vectors numCpMv as input,the control point motion vector predictor candidates cpMvpLX[cpIdx] withcpIdx=0 . . . numCpMv−1 as output.

The rounding process for motion vectors as specified in clause 8.4.2.14is invoked with mvX set equal to cpMvpLX[cpIdx], rightShift set equal to(MvShift+2), and leftShift set equal to (MvShift+2) as inputs and therounded cpMvpLX[cpIdx] with cpIdx=0 . . . numCpMv−1 as output.

The following assignments are made:

cpMvpListLX[numCpMvpCandLX][0]=cpMvpLX[0]  (8-618)

cpMvpListLX[numCpMvpCandLX][1]=cpMvpLX[1]  (8-619)

cpMvpListLX[numCpMvpCandLX][2]=cpMvpLX[2]  (8-620)

numCpMvpCandLX=numCpMvpCandLX+1  (8-621)

Otherwise if PredFlagLY[xNbBk][yNbBk] (with Y=!X) is equal to 1 andDiffPicOrderCnt(RefPicListY[RefIdxLY[xNbBk][yNbBk]],RefPicListX[refIdxLX]) is equal to 0, the following applies:

The variable availableFlagB is set equal to TRUE The derivation processfor luma affine control point motion vectors from a neighbouring blockas specified in clause 8.4.4.5 is invoked with the luma coding blocklocation (xCb, yCb), the luma coding block width and height (cbWidth,cbHeight), the neighbouring luma coding block location (xNb, yNb), theneighbouring luma coding block width and height (nbW, nbH), and thenumber of control point motion vectors numCpMv as input, the controlpoint motion vector predictor candidates cpMvpLY[cpIdx] with cpIdx=0 . .. numCpMv−1 as output.

The rounding process for motion vectors as specified in clause 8.4.2.14is invoked with mvX set equal to cpMvpLY[cpIdx], rightShift set equal to(MvShift+2), and leftShift set equal to (MvShift+2) as inputs and therounded cpMvpLY[cpIdx] with cpIdx=0 . . . numCpMv−1 as output.

The following assignments are made:

cpMvpListLX[numCpMvpCandLX][0]=cpMvpLY[0]  (8-622)

cpMvpListLX[numCpMvpCandLX][1]=cpMvpLY[1]  (8-623)

cpMvpListLX[numCpMvpCandLX][2]=cpMvpLY[2]  (8-624)

numCpMvpCandLX=numCpMvpCandLX+1  (8-625)

When numCpMvpCandLX is less than 2, the following applies

The derivation process for constructed affine control point motionvector prediction candidate as specified in clause 8.4.4.8 is invokedwith the luma coding block location (xCb, yCb), the luma coding blockwidth cbWidth, the luma coding block height cbHeight, and the referenceindex of the current coding unit refIdxLX as inputs, and theavailability flag availableConsFlagLX, the availability flagsavailableFlagLX[cpIdx] and cpMvpLX[cpIdx] with cpIdx=0 . . . numCpMv−1as outputs.

When availableConsFlagLX is equal to 1, and numCpMvpCandLX is equal to0, the following assignments are made:

cpMvpListLX[numCpMvpCandLX][0]=cpMvpLX[0]  (8-626)

cpMvpListLX[numCpMvpCandLX][1]=cpMvpLX[1]  (8-627)

cpMvpListLX[numCpMvpCandLX][2]=cpMvpLX[2]  (8-628)

numCpMvpCandLX=numCpMvpCandLX+1  (8-629)

The following applies for cpIdx=0 . . . numCpMv−1:

When numCpMvpCandLX is less than 2 and availableFlagLX[cpIdx] is equalto 1, the following assignments are made:

cpMvpListLX[numCpMvpCandLX][0]=cpMvpLX[cpIdx]  (8-630)

cpMvpListLX[numCpMvpCandLX][1]=cpMvpLX[cpIdx]  (8-631)

cpMvpListLX[numCpMvpCandLX][2]=cpMvpLX[cpIdx]  (8-632)

numCpMvpCandLX=numCpMvpCandLX+1  (8-633)

When numCpMvpCandLX is less than 2, the following applies:

The derivation process for temporal luma motion vector prediction asspecified in clause 8.4.2.11 is with the luma coding block location(xCb, yCb), the luma coding block width cbWidth, the luma coding blockheight cbHeight and refIdxLX as inputs, and with the output being theavailability flag availableFlagLXCol and the temporal motion vectorpredictor mvLXCol.

When availableFlagLXCol is equal to 1, the following applies:

The rounding process for motion vectors as specified in clause 8.4.2.14is invoked the with mvX set equal to mvLXCol, rightShift set equal to(MvShift+2), and leftShift set equal to (MvShift+2) as inputs and therounded mvLXCol as output.

The following assignments are made:

cpMvpListLX[numCpMvpCandLX][0]=mvLXCol  (8-634)

cpMvpListLX[numCpMvpCandLX][1]=mvLXCol  (8-635)

cpMvpListLX[numCpMvpCandLX][2]=mvLXCol  (8-636)

numCpMvpCandLX=numCpMvpCandLX+1  (8-637)

When numCpMvpCandLX is less than 2, the following is repeated untilnumCpMvpCandLX is equal to 2, with mvZero[0] and mvZero[1] both beingequal to 0:

cpMvpListLX[numCpMvpCandLX][0]=mvZero  (8-638)

cpMvpListLX[numCpMvpCandLX][1]=mvZero  (8-639)

cpMvpListLX[numCpMvpCandLX][2]=mvZero  (8-640)

numCpMvpCandLX=numCpMvpCandLX+1  (8-641)

The affine control point motion vector predictor cpMvpLX with X being 0or 1 is derived as follows:

cpMvpLX=cpMvpListLX[mvp_1X_flag[xCb][yCb]]  (8-642)

Derivation Process for Constructed Affine Control Point Motion VectorPrediction Candidates

Inputs to this process are:

-   -   a luma location (xCb, yCb) specifying the top-left sample of the        current luma coding block relative to the top-left luma sample        of the current picture,    -   two variables cbWidth and cbHeight specifying the width and the        height of the current luma coding block,    -   the reference index of the current prediction unit partition        refIdxLX, with X being 0 or 1,        Output of this process are:    -   the availability flag of the constructed affine control point        motion vector prediction candidates availableConsFlagLX with X        being 0 or 1,    -   the availability flags availableFlagLX[cpIdx] with cpIdx=0 . . .        2 and X being 0 or 1,    -   the constructed affine control point motion vector prediction        candidates cpMvLX[cpIdx] with cpIdx=0 . . . numCpMv−1 and X        being 0 or 1.

The first (top-left) control point motion vector cpMvLX[0] and theavailability flag availableFlagLX[0] are derived in the followingordered steps:

The sample locations (xNbB2, yNbB2), (xNbB3, yNbB3) and (xNbA2, yNbA2)are set equal to (xCb−1, yCb−1), (xCb, yCb−1) and (xCb−1, yCb),respectively.

The availability flag availableFlagLX[0] is set equal to 0 and bothcomponents of cpMvLX[0] are set equal to 0.

The following applies for (xNbTL, yNbTL) with TL being replaced by B2,B3, and A2:

The availability derivation process for a coding block as specified inclause is invoked with the luma coding block location (xCb, yCb), theluma coding block width cbWidth, the luma coding block height cbHeight,the luma location (xNbY, yNbY) set equal to (xNbTL, yNbTL) as inputs,and the output is assigned to the coding block availability flagavailableTL.

When availableTL is equal to TRUE and availableFlagLX[0] is equal to 0,the following applies:

If PredFlagLX[xNbTL][yNbTL] is equal to 1, andDiffPicOrderCnt(RefPicListX[RefIdxLX[xNbTL][yNbTL]],RefPicListX[refIdxLX]) is equal to 0, and the reference picturecorresponding to RefIdxLX[xNbTL][yNbTL] is not the current picture,availableFlagLX[0] is set equal to 1 and the following assignments aremade:

cpMvLX[0]=MvLX[xNbTL][yNbTL]  (8-643)

Otherwise, when PredFlagLY[xNbTL][yNbTL] (with Y=!X) is equal to 1 andDiffPicOrderCnt(RefPicListY[RefIdxLY[xNbTL][yNbTL]],RefPicListX[refIdxLX]) is equal to 0, and the reference picturecorresponding to RefIdxLY[xNbTL][yNbTL] is not the current picture,availableFlagLX[0] is set equal to 1 and the following assignments aremade:

cpMvLX[0]=MvLY[xNbTL][yNbTL]  (8-644)

When availableFlagLX[0] is equal to 1, the rounding process for motionvectors as specified in clause 8.4.2.14 is invoked with mvX set equal tocpMvLX[0], rightShift set equal to (MvShift+2), and leftShift set equalto (MvShift+2) as inputs and the rounded cpMvLX[0] as output.

The second (top-right) control point motion vector cpMvLX[1] and theavailability flag availableFlagLX[1] are derived in the followingordered steps:

The sample locations (xNbB1, yNbB1) and (xNbB0, yNbB0) are set equal to(xCb+cbWidth−1, yCb−1) and (xCb+cbWidth, yCb−1), respectively.

The availability flag availableFlagLX[1] is set equal to 0 and bothcomponents of cpMvLX[1] are set equal to 0.

The following applies for (xNbTR, yNbTR) with TR being replaced by B1and B0:

The availability derivation process for a coding block as specified inclause 6.4.X is invoked with the luma coding block location (xCb, yCb),the luma coding block width cbWidth, the luma coding block heightcbHeight, the luma location (xNbY, yNbY) set equal to (xNbTR, yNbTR) asinputs, and the output is assigned to the coding block availability flagavailableTR.

When availableTR is equal to TRUE and availableFlagLX[1] is equal to 0,the following applies:

If PredFlagLX[xNbTR][yNbTR] is equal to 1, andDiffPicOrderCnt(RefPicListX[RefIdxLX[xNbTR][yNbTR]],RefPicListX[refIdxLX]) is equal to 0, and the reference picturecorresponding to RefIdxLX[xNbTR][yNbTR] is not the current picture,availableFlagLX[1] is set equal to 1 and the following assignments aremade:

cpMvLX[1]=MvLX[xNbTR][yNbTR]  (8-645)

Otherwise, when PredFlagLY[xNbTR][yNbTR] (with Y=!X) is equal to 1 andDiffPicOrderCnt(RefPicListY[RefIdxLY[xNbTR][yNbTR]],RefPicListX[refIdxLX]) is equal to 0, and the reference picturecorresponding to RefIdxLY[xNbTR][yNbTR] is not the current picture,availableFlagLX[1] is set equal to 1 and the following assignments aremade:

cpMvLX[1]=MvLY[xNbTR][yNbTR]  (8-646)

When availableFlagLX[1] is equal to 1, the rounding process for motionvectors as specified in clause 8.4.2.14 is invoked with mvX set equal tocpMvLX[1], rightShift set equal to (MvShift+2), and leftShift set equalto (MvShift+2) as inputs and the rounded cpMvLX[1] as output.

The third (bottom-left) control point motion vector cpMvLX[2] and theavailability flag availableFlagLX[2] are derived in the followingordered steps:

The sample locations (xNbA1, yNbA1) and (xNbA0, yNbA0) are set equal to(xCb−1, yCb+cbHeight−1) and (xCb−1, yCb+cbHeight), respectively.

The availability flag availableFlagLX[2] is set equal to 0 and bothcomponents of cpMvLX[2] are set equal to 0.

The following applies for (xNbBL, yNbBL) with BL being replaced by A1and A0:

The availability derivation process for a coding block as specified inclause 6.4.X invoked with the luma coding block location (xCb, yCb), theluma coding block width cbWidth, the luma coding block height cbHeight,the luma location (xNbY, yNbY) set equal to (xNbBL, yNbBL) as inputs,and the output is assigned to the coding block availability flagavailableBL.

When availableBL is equal to TRUE and availableFlagLX[2] is equal to 0,the following applies:

If PredFlagLX[xNbBL][yNbBL] is equal to 1, andDiffPicOrderCnt(RefPicListX[RefIdxLX[xNbBL][yNbBL]],RefPicListX[refIdxLX]) is equal to 0, and the reference picturecorresponding to RefIdxLY[xNbBL][yNbBL] is not the current picture,availableFlagLX[2] is set equal to 1 and the following assignments aremade:

cpMvLX[2]=MvLX[xNbBL][yNbBL]  (8-647)

Otherwise, when PredFlagLY[xNbBL][yNbBL] (with Y=!X) is equal to 1 andDiffPicOrderCnt(RefPicListY[RefIdxLY[xNbBL][yNbBL]],RefPicListX[refIdxLX]) is equal to 0, and the reference picturecorresponding to RefIdxLY[xNbBL][yNbBL] is not the current picture,availableFlagLX[2] is set equal to 1 and the following assignments aremade:

cpMvLX[2]=MvLY[xNbBL][yNbBL]  (8-648)

When availableFlagLX[2] is equal to 1, the rounding process for motionvectors as specified in clause 8.4.2.14 is invoked with mvX set equal tocpMvLX[2], rightShift set equal to (MvShift+2), and leftShift set equalto (MvShift+2) as inputs and the rounded cpMvLX[2] as output.

1.5. Context Modeling

Assignment of ctxInc to syntax elements with context coded bins:

binIdx Syntax element 0 1 2 3 4 >=5 amvr_flag[ ][ ] 0, 1, 2 na na na nana (clause 9.5.4.2.2, when inter_affine_flag[ ][ ] is equal to 0)amvr_coarse_precisoin_flag[ ][ ] 0 na na na na naSpecification of ctxInc using left and above syntax elements:

In one example, context increasement offset ctxInc=(condL &&availableL)+(condA && availableA)+ctxSetIdx*3.

Alternatively, ctxInc=((condL && availableL) (condA &&availableA))+ctxSetIdx*3.

ctxInc=(condL && availableL)+M*(condA && availableA)+ctxSetIdx*3. (e.g.,M=2)

ctxInc=M*(condL && availableL)+(condA && availableA)+ctxSetIdx*3. (e.g.,M=2)

Syntax element condL condA ctxSetIdx e cu_skip_flag cu_skip_flag 0 [xNbL ][ yNbL ] [ xNbA ][ yNbA ] e !inter_affine_flag !inter_affine_flag0 [ x0 ][ y0 ] && [ x0 ][ y0 ] && amvr_flag amvr_flag [ xNbL ][ yNbL ] [xNbA ][ yNbA]

Values of initValue for ctxIdx of amvr_flag:

Different contexts are used when current block is affine or non-affine.

ctxIdx of amvr_flag ctxIdx of amvr_flag when inter_affine_flag wheninter_affine_ Initialization is equal to 0 flag is equal to 1 variable 01 2 3 initValue xx xx xx xx

Alternatively,

ctxIdx of amvr_flag ctxIdx of amvr_flag when inter_affine_flag wheninter_affine_flag Initialization is equal to 0 is equal to 1 variable 01 initValue xx xx

Alternatively, same contexts may be used when current block is affine ornon-affine.

ctxIdx of amvr_flag ctxIdx of amvr_flag when inter_affine_flag wheninter_affine_flag Initialization is equal to 0 is equal to 1 variable 00 initValue xx xx

Alternatively, amvr_flag is bypass coded.

Values of initValue for ctxIdx of amvr_coarse_precision_flag:

Different contexts are used when current block is affine or non-affine.

ctxIdx of ctxIdx of amvr_coarse_precisoin_flagamvr_coarse_precisoin_flag when inter_affine_flag when inter_affine_flagInitialization is equal to 0 is equal to 1 variable 0 0 initValue xxx xx

Alternatively,

ctxIdx of ctxIdx of amvr_coarse_precisoin_flagamvr_coarse_precisoin_flag Initialization when inter_affine_flag wheninter_affine_flag variable is equal to 0 is equal to 1 initValue xxx xx

Alternatively, same contexts may be used when current block is affine ornon-affine.

ctxIdx of Initialization amvr_coarse_precisoin_flag variable 0 initValuexxx

Alternatively, amvr_coarse_precision_flag is bypass coded.

The examples described above may be incorporated in the context of themethod described below, e.g., methods 2510 to 2540, which may beimplemented at a video decoder or a video encoder.

FIGS. 25A to 25D show flowcharts of exemplary methods for videoprocessing. The method 2510 as shown in FIG. 25A includes, at step 2512,determining that a conversion between a current video block of a videoand a coded representation of the current video block is based on anon-affine inter AMVR mode. The method 2510 further includes, at step2514, performing the conversion based on the determining. In someimplementations, the coded representation of the current video block isbased on a context based coding, and wherein a context used for codingthe current video block is modeled without using an affine AMVR modeinformation of a neighboring block during the conversion

The method 2520 as shown in FIG. 25B includes, at step 2522, determiningthat a conversion between a current video block of a video and a codedrepresentation of the current video block is based on an affine adaptivemotion vector resolution (affine AMVR) mode. The method 2520 furtherincludes, at step 2524, performing the conversion based on thedetermining. In some implementations, the coded representation of thecurrent video block is based on a context based coding, and wherein avariable controls two probability updating speeds for a context.

The method 2530 as shown in FIG. 25C includes, at step 2532, determiningthat a conversion between a current video block of a video and a codedrepresentation of the current video block is based on an affine AMVRmode. The method 2530 further includes, at step 2534, performing theconversion based on the determining. In some implementations, the codedrepresentation of the current video block is based on a context basedcoding, and wherein a context used for coding the current video block ismodeled using a coding information of a neighboring block for which anAMVR mode of both affine inter mode and normal inter mode is used duringthe conversion.

The method 2540 as shown in FIG. 25D includes, at step 2542,determining, for a conversion between a current video block of a videoand a coded representation of the current video block, a usage ofmultiple contexts for the conversion. The method 2540 further includes,at step 2544, performing the conversion based on the determining. Insome implementations, the multiple contexts are utilized for coding asyntax element indicating a coarse motion precision.

The method 2550 as shown in FIG. 25E includes, at step 2552, making adetermination, for a conversion between a current video block of a videoand a coded representation of the current video block, whether to use asymmetric motion vector difference (SMVD) mode based on a currentlyselected best mode for the conversion. The method 2554 further includes,performing the conversion based on the determining.

The method 2560 as shown in FIG. 25F includes, at step 2562, making adetermining, for a conversion between a current video block of a videoand a coded representation of the current video block, whether to use anaffine SMVD mode based on a currently selected best mode for theconversion. The method 2564 further includes, performing the conversionbased on the determining.

5. Example Implementations of the Disclosed Technology

FIG. 26 is a block diagram of a video processing apparatus 2600. Theapparatus 2600 may be used to implement one or more of the methodsdescribed herein. The apparatus 2600 may be embodied in a smartphone,tablet, computer, Internet of Things (IoT) receiver, and so on. Theapparatus 2600 may include one or more processors 2602, one or morememories 2604 and video processing hardware 2606. The processor(s) 2602may be configured to implement one or more methods (including, but notlimited to, method 2500) described in the present document. The memory(memories) 2604 may be used for storing data and code used forimplementing the methods and techniques described herein. The videoprocessing hardware 2606 may be used to implement, in hardwarecircuitry, some techniques described in the present document.

FIG. 28 is another example of a block diagram of a video processingsystem in which disclosed techniques may be implemented. FIG. 28 is ablock diagram showing an example video processing system 2800 in whichvarious techniques disclosed herein may be implemented. Variousimplementations may include some or all of the components of the system2800. The system 2800 may include input 2802 for receiving videocontent. The video content may be received in a raw or uncompressedformat, e.g., 8 or 10 bit multi-component pixel values, or may be in acompressed or encoded format. The input 2802 may represent a networkinterface, a peripheral bus interface, or a storage interface. Examplesof network interface include wired interfaces such as Ethernet, passiveoptical network (PON), etc. and wireless interfaces such as Wi-Fi orcellular interfaces.

The system 2800 may include a coding component 2804 that may implementthe various coding or encoding methods described in the presentdocument. The coding component 2804 may reduce the average bitrate ofvideo from the input 2802 to the output of the coding component 2804 toproduce a coded representation of the video. The coding techniques aretherefore sometimes called video compression or video transcodingtechniques. The output of the coding component 2804 may be eitherstored, or transmitted via a communication connected, as represented bythe component 2806. The stored or communicated bitstream (or coded)representation of the video received at the input 2902 may be used bythe component 2808 for generating pixel values or displayable video thatis sent to a display interface 2810. The process of generatinguser-viewable video from the bitstream representation is sometimescalled video decompression. Furthermore, while certain video processingoperations are referred to as “coding” operations or tools, it will beappreciated that the coding tools or operations are used at an encoderand corresponding decoding tools or operations that reverse the resultsof the coding will be performed by a decoder.

Examples of a peripheral bus interface or a display interface mayinclude universal serial bus (USB) or high definition multimediainterface (HDMI) or Displayport, and so on. Examples of storageinterfaces include SATA (serial advanced technology attachment), PCI,IDE interface, and the like. The techniques described in the presentdocument may be embodied in various electronic devices such as mobilephones, laptops, smartphones or other devices that are capable ofperforming digital data processing and/or video display.

In some embodiments, the video coding methods may be implemented usingan apparatus that is implemented on a hardware platform as describedwith respect to FIG. 26 or 28.

Various techniques and embodiments may be described using the followingclause-based format. These clauses may be implemented as preferredfeatures of some embodiments.

A first set of clauses use some of the techniques described in theprevious section, including, for example, items 16-18, 23, and 26 in theprevious section.

1. A method for video processing, comprising: determining that aconversion between a current video block of a video and a codedrepresentation of the current video block is based on a non-affine interAMVR mode; and performing the conversion based on the determining, andwherein the coded representation of the current video block is based ona context based coding, and wherein a context used for coding thecurrent video block is modeled without using an affine AMVR modeinformation of a neighboring block during the conversion.

2. The method of clause 1, wherein a non-affine inter AMVR mode index ofthe neighboring block coded is utilized.

3. The method of clause 2, wherein a context index used for coding thenon-affine inter AMVR mode index of the current video block is dependenton at least one of an AMVR mode index, an affine mode flag, or anavailability of left and above neighboring blocks, the non-affine interAMVR mode index indicating a certain MVD precision.

4. The method of clause 3, wherein offset values are derived for theleft neighboring block and the above neighboring block, respectively,and the context index is derived as the sum of the offset values of theleft neighboring block and the above neighboring block.

5. The method of clause 4, wherein at least one of the offset values isderived as 1 in case that a corresponding neighboring block is availableand is not coded in an affine mode and the AMVR mode index of theneighboring block is not equal to 0, and the at least one of the offsetvalues is derived as 0 otherwise.

6. The method of clause 1, wherein affine AMVR mode information of theneighboring block is not directly used but indirectly used with afunction of the affine AMVR mode information.

7. The method of clause 6, wherein the function returns true in a casethat amvr_mode[xNbL][yNbL] or amvr_flag[xNbL][yNbL] of the neighboringblock covering (xNbL, yNbL) indicates a certain MVD precision.

8. The method of clause 1, wherein the affine AMVR mode information ofthe neighboring block is utilized for coding a first syntax element of anon-affine inter AMVR mode of the current video block.

9. The method of clause 1, wherein, in a case that an AMVR mode of thecurrent video block is represented by multiple syntax elements, AMVRmode information of the neighboring block coded in both non-affine intermode and affine inter mode is utilized for coding any one of themultiple syntax elements.

10. The method of clause 1, wherein, in a case that an AMVR mode of thecurrent video block is represented by multiple syntax elements, AMVRmode information of the neighboring block coded in affine inter mode isnot utilized for coding any one of the multiple syntax elements.

11. The method of clause 1, wherein, in a case that an AMVR mode of thecurrent video block is represented by multiple syntax elements, AMVRmode information of the neighboring block coded in affine inter mode isnot directly utilized but indirectly used for coding any one of themultiple syntax elements.

12. The method of any of clauses 9-11, wherein, the AMVR mode of thecurrent video block includes affine inter AMVR mode and non-affine interAMVR mode.

13. A method for video processing, comprising: determining that aconversion between a current video block of a video and a codedrepresentation of the current video block is based on an affine adaptivemotion vector resolution (affine AMVR) mode; and performing theconversion based on the determining, and wherein the codedrepresentation of the current video block is based on a context basedcoding, and wherein a variable controls two probability updating speedsfor a context.

14. The method of clause 13, wherein the two probability updating speedsinclude a faster updating speed defined by (shiftIdx>>2)+2, shiftIdxindicating the variable.

15. The method of clause 13, wherein the two probability updating speedsinclude a slower updating speed defined by (shiftIdx & 3)+3+shift0,shift0 defined by (shiftIdx>>2)+2 and shiftIdx indicating the variable.

16. The method of clause 14, wherein the faster updating speed isbetween 2 and 5.

17. A method for video processing, comprising: determining that aconversion between a current video block of a video and a codedrepresentation of the current video block is based on an affine AMVRmode; and performing the conversion based on the determining, andwherein the coded representation of the current video block is based ona context based coding, and wherein a context used for coding thecurrent video block is modeled using a coding information of aneighboring block for which an AMVR mode of both affine inter mode andnormal inter mode is used during the conversion.

18. The method of clause 17, wherein AMVR mode information of theneighboring block is directly used for the context based coding.

19. The method of clause 17, wherein AMVR mode information of theneighboring block coded in normal inter mode is disallowed for thecontext based coding.

20. The method of clause 17, wherein AMVR mode information of theneighboring block coded in normal inter mode is not directly used butindirectly used with a function of the AMVR mode information.

21. The method of clause 17, wherein AMVR mode information of theneighboring block is utilized for coding a first syntax element of theaffine AMVR mode of the current video block.

22. The method of clause 17, wherein, in a case that the affine AMVRmode is represented by multiple syntax elements, AMVR mode informationof the neighboring block coded in both affine inter mode and normalinter mode is utilized for coding any one of the multiple syntaxelements.

23. The method of clause 17, wherein, in a case that the affine AMVRmode is represented by multiple syntax elements, AMVR mode informationof the neighboring block coded in normal inter mode is not utilized forcoding any one of the multiple syntax elements.

24. The method of clause 17, wherein, in a case that the affine AMVRmode is represented by multiple syntax elements, AMVR mode informationof the neighboring block coded in normal inter mode is not directlyutilized but indirectly used for coding any one of the multiple syntaxelements.

25. A method for video processing, comprising: determining, for aconversion between a current video block of a video and a codedrepresentation of the current video block, a usage of multiple contextsfor the conversion; and performing the conversion based on thedetermining, and wherein the multiple contexts are utilized for coding asyntax element indicating a coarse motion precision.

26. The method of clause 25, wherein the multiple contexts correspond toexactly two contexts.

27. The method of clause 26, wherein the multiple contexts are selectedbased on whether the current video block is affine coded.

28. The method of clause 25, wherein another syntax element is used toindicate that the conversion is based on an affine AMVR mode.

29. The method of clause 28, wherein the another syntax element is codedwith only a first context and the syntax element is coded with only asecond context.

30. The method of clause 28, wherein the another syntax element is codedwith only a first context and the syntax element is bypass coded.

31. The method of clause 28, wherein the another syntax element isbypass coded and the syntax element is bypass coded.

32. The method of clause 25, wherein all syntax elements related tomotion vector precisions are bypass coded.

33. The method of clause 25 or 26, wherein the syntax element indicatesa selection from a set including 1-pel or 4-pel precision for the normalinter mode.

34. The method of clause 25 or 26, wherein the syntax element indicatesa selection from at least between 1/16-pel or 1-pel precision for theaffine mode.

35. The method of clause 34, wherein the syntax element is equal to 0,⅙-pel precision for the affine mode.

36. The method of clause 34, wherein the syntax element is equal to 1,1-pel precision for the affine mode.

37. The method of any of clauses 1 to 36, wherein the performing of theconversion includes generating the coded representation from the currentvideo block.

38. The method of any of clauses 1 to 36, wherein the performing of theconversion includes generating the current video block from the codedrepresentation.

39. An apparatus in a video system comprising a processor and anon-transitory memory with instructions thereon, wherein theinstructions upon execution by the processor, cause the processor toimplement the method in any one of clauses 1 to 38.

40. A computer program product stored on a non-transitory computerreadable media, the computer program product including program code forcarrying out the method in any one of clauses 1 to 38.

A second set of clauses use some of the techniques described in theprevious section, including, for example, items 19-21 and 23 in theprevious section.

1. A method of video processing, comprising: making a determination, fora conversion between a current video block of a video and a codedrepresentation of the current video block, whether to use a symmetricmotion vector difference (SMVD) mode based on a currently selected bestmode for the conversion; and performing the conversion based on thedetermining.

2. The method of clause 1, wherein the SMVD mode is used withoutexplicit signaling of at least one reference index of reference list.

3. The method of clause 2, wherein the reference index is derived basedrecursive picture order count (POC) calculation.

4. The method of clause 1, wherein, in a case that the currentlyselected best mode is a merge mode or a UMVE mode, the determiningdisables the usage of the SMVD mode.

5. The method of clause 4, wherein the UMVE mode applies a motion vectoroffset to refine a motion candidate derived from a merge candidate list.

6. The method of clause 1, wherein, in a case that the currentlyselected best mode is not coded with the SMVD mode, the determiningdisables the usage of the SMVD mode.

7. The method of clause 1, wherein, in a case that the currentlyselected best mode is an affine mode, the determining disables the usageof the SMVD mode.

8. The method of clause 1, wherein, in a case that the currentlyselected best mode is a sub-block merge mode, the determining disablesthe usage of the SMVD mode.

9. The method of clause 1, wherein, in a case that the currentlyselected best mode is an affine SMVD mode, the determining disables theusage of the SMVD mode.

10. The method of clause 1, wherein, in a case that the currentlyselected best mode is an affine merge mode, the determining disables theusage of the SMVD mode.

11. The method of any of clauses 2-10, wherein the determining isapplied only when a MVD (motion vector differences) precision is greaterthan or equal to a precision.

12. The method of any of clauses 2-10, wherein the determining isapplied only when a MVD precision is greater than a precision.

13. The method of any of clauses 2-10, wherein the determining isapplied only when MVD precision is smaller than or equal to a precision.

14. The method of any of clauses 2-10, wherein the determining isapplied only when MVD precision is smaller than a precision.

15. A method for video processing, comprising: making a determining, fora conversion between a current video block of a video and a codedrepresentation of the current video block, whether to use an affine SMVDmode based on a currently selected best mode for the conversion; andperforming the conversion based on the determining.

16. The method of clause 15, wherein, in a case that the currentlyselected best mode is a merge mode or a UMVE mode, the determiningdisables the usage of the affine SMVD mode.

17. The method of clause 15, wherein, in a case that the currentlyselected best mode is not coded with the affine SMVD mode, thedetermining disables the usage of the affine SMVD mode.

18. The method of clause 15, wherein, in a case that the currentlyselected best mode is a sub-block merge mode, the determining disablesthe usage of the affine SMVD mode.

19. The method of clause 15, wherein, in a case that the currentlyselected best mode is an SMVD mode, the determining disables the usageof the affine SMVD mode.

20. The method of clause 15, wherein, in a case that the currentlyselected best mode is an affine merge mode, the determining disables theusage of the affine SMVD mode.

21. The method of any of clauses 16-20, wherein the determining isapplied only when an affine MVD precision is greater than or equal to aprecision.

22. The method of any of clauses 16-20, wherein the determining isapplied only when an affine MVD precision is greater than a precision.

23. The method of any of clauses 16-20, wherein the determining isapplied only when an affine MVD precision is smaller than or equal to aprecision.

24. The method of any of clauses 16-20, wherein the determining isapplied only when am affine MVD precision is smaller than a precision.

25. The method of clause 1 or 15, further comprising: determiningcharacteristics of the current video block, the characteristicsincluding one or more of: a block size of the video block, a slice orpicture or tile type of the video block, or motion information relatedto the video block, and wherein the determining is also based on thecharacteristics.

26. The method of any of clauses 1 to 25, wherein the performing of theconversion includes generating the coded representation from the currentblock.

27. The method of any of clauses 1 to 25, wherein the performing of theconversion includes generating the current block from the codedrepresentation.

28. An apparatus in a video system comprising a processor and anon-transitory memory with instructions thereon, wherein theinstructions upon execution by the processor, cause the processor toimplement the method in any one of clauses 1 to 27.

29. A computer program product stored on a non-transitory computerreadable media, the computer program product including program code forcarrying out the method in any one of clauses 1 to 27.

From the foregoing, it will be appreciated that specific embodiments ofthe presently disclosed technology have been described herein forpurposes of illustration, but that various modifications may be madewithout deviating from the scope of the invention. Accordingly, thepresently disclosed technology is not limited except as by the appendedclaims.

Implementations of the subject matter and the functional operationsdescribed in this patent document can be implemented in various systems,digital electronic circuitry, or in computer software, firmware, orhardware, including the structures disclosed in this specification andtheir structural equivalents, or in combinations of one or more of them.Implementations of the subject matter described in this specificationcan be implemented as one or more computer program products, i.e., oneor more modules of computer program instructions encoded on a tangibleand non-transitory computer readable medium for execution by, or tocontrol the operation of, data processing apparatus. The computerreadable medium can be a machine-readable storage device, amachine-readable storage substrate, a memory device, a composition ofmatter effecting a machine-readable propagated signal, or a combinationof one or more of them. The term “data processing unit” or “dataprocessing apparatus” encompasses all apparatus, devices, and machinesfor processing data, including by way of example a programmableprocessor, a computer, or multiple processors or computers. Theapparatus can include, in addition to hardware, code that creates anexecution environment for the computer program in question, e.g., codethat constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Computer readable media suitable for storingcomputer program instructions and data include all forms of nonvolatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

It is intended that the specification, together with the drawings, beconsidered exemplary only, where exemplary means an example. As usedherein, the use of “or” is intended to include “and/or”, unless thecontext clearly indicates otherwise.

While this patent document contains many specifics, these should not beconstrued as limitations on the scope of any invention or of what may beclaimed, but rather as descriptions of features that may be specific toparticular embodiments of particular inventions. Certain features thatare described in this patent document in the context of separateembodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Moreover, the separation of various system components in theembodiments described in this patent document should not be understoodas requiring such separation in all embodiments.

Only a few implementations and examples are described and otherimplementations, enhancements and variations can be made based on whatis described and illustrated in this patent document.

What is claimed is:
 1. A method for video processing, comprising:determining, for a conversion between a current video block of a videoand a bitstream of the video, at least one syntax element of which atleast one bin is context-coded for the current video block; determininga context increasement value for the at least one bin; determining avariable for the context increasement value; and performing theconversion at least based on the variable; wherein the variable controlstwo probability updating speeds for context.
 2. The method of claim 1,wherein the at least one syntax element in the bitstream is used toindicate a motion precision in a motion precision set; and wherein thecontext is selected from multiple contexts for the at least one syntaxelement based on a coding mode of the current video block.
 3. The methodof claim 2, wherein multiple syntax elements are selectively presentedin the bitstream to indicate the motion precision in the motionprecision set, wherein the multiple syntax elements include a firstsyntax element and a second syntax element, wherein the second syntaxelement is present in the bitstream in case that the first syntaxelement is present in the bitstream with a specific value; and whereinthe at least one syntax element comprises the first syntax elementand/or the second syntax element.
 4. The method of claim 2, wherein thecontext increasement value is selected from the multiple contextincreasement values based on whether the coding mode of the currentvideo block is a first mode, and wherein in the first mode, controlpoint motion vectors are derived and further used to derive motionvectors of sub-region split from the current video block.
 5. The methodof claim 1, wherein the context increasement value is selected withoutusing coding information of a neighboring video block of the currentvideo block, and the coding information of the neighboring video blockcomprises a coding mode of the neighboring video block.
 6. The method ofclaim 1, wherein the two probability updating speeds include a firstupdating speed defined by (shiftIdx>>2)+2, shiftIdx indicating thevariable.
 7. The method of claim 1, wherein the two probability updatingspeeds include a second updating speed defined by (shiftIdx &3)+3+shift0, shift0 indicating a first updating speed and shiftIdxindicating the variable.
 8. The method of claim 7, wherein the firstupdating speed is greater than or equal to
 2. 9. The method of claim 7,wherein the first updating speed is smaller than or equal to
 5. 10. Themethod of claim 3, wherein the second syntax element indicates aselection from 1-pel, ½-pel, or 4-pel precision for a normal inter mode,and the second syntax element indicates a selection from 1/16-pel or1-pel precision for a first mode, and wherein in the first mode, controlpoint motion vectors are derived and further used to derive motionvectors of sub-region split from the current video block.
 11. The methodof claim 3, wherein the second syntax element is equal to 0, and themotion precision is 1/16-pel precision for a first mode, and wherein thesecond syntax element is equal to 1, and the motion precision is 1-pelprecision for a first mode, and wherein in the first mode, control pointmotion vectors are derived and further used to derive motion vectors ofsub-region split from the current video block.
 12. The method of claim1, wherein the performing of the conversion includes generating thebitstream based on the current video block.
 13. The method of claim 1,wherein the performing of the conversion includes generating the currentvideo block from the bitstream.
 14. An apparatus for processing videodata comprising a processor and a non-transitory memory withinstructions thereon, wherein the instructions upon execution by theprocessor, cause the processor to: determine, for a conversion between acurrent video block of a video and a bitstream of the video, at leastone syntax element of which at least one bin is context-coded for thecurrent video block; determine a context increasement value for the atleast one bin; determine a variable for the context increasement value;and perform the conversion at least based on the variable; wherein thevariable controls two probability updating speeds for the context. 15.The apparatus of claim 14, wherein the two probability updating speedsinclude a first updating speed defined by (shiftIdx>>2)+2, shiftIdxindicating the variable.
 16. The apparatus of claim 14, wherein the twoprobability updating speeds include a second updating speed defined by(shiftIdx & 3)+3+shift0, shift0 indicating a first updating speed andshiftIdx indicating the variable.
 17. The apparatus of claim 15, whereinthe first updating speed is greater than or equal to
 2. 18. Theapparatus of claim 15, wherein the first updating speed is smaller thanor equal to
 5. 19. A non-transitory computer-readable storage mediumstoring instructions that cause a processor to: determine, for aconversion between a current video block of a video and a bitstream ofthe video, at least one syntax element of which at least one bin iscontext-coded for the current video block; determine a contextincreasement value for the at least one bin; determine a variable forthe context increasement value; and perform the conversion at leastbased on the variable; wherein the variable controls two probabilityupdating speeds for the context.
 20. A non-transitory computer-readablerecording medium storing a bitstream of a video which is generated by amethod performed by a video processing apparatus, wherein the methodcomprises: determining, for a current video block of the video, at leastone syntax element of which at least one bin is context-coded;determining a context increasement value for the at least one bin;determining a variable for the context increasement value; andgenerating the bitstream at least based on the variable; wherein thevariable controls two probability updating speeds for the context.